To compare two PDF files, you can use an online tool like PDF.net that will highlight the differences and similarities between documents easily.

The easiest way to compare two PDF files is to 

upload both documents to an online PDF comparison tool and let it highlight every difference automatically

. This beats switching between two open windows and scanning each page by eye, since small edits are easy to miss that way.

Comparing documents can be necessary for both professional and personal use, but doing this manually can take a lot of time, and human error and inconsistencies may be a common issue in such cases. Because of this, it’s best to use a PDF file comparison tool to ensure efficiency and accuracy.

This guide covers how to compare two PDF files with pdf.net, when to choose side-by-side versus overlay comparison, and what to do when you're working with a scanned document.

Compare your PDFs in seconds!

Upload both PDF versions to pdf.net's comparison tool, then choose side-by-side or overlay comparison depending on what you need to check.

Side-by-side comparison highlights added, deleted, and replaced text, while overlay comparison is better for spotting layout and visual changes.

Comparing two PDF files helps you review contract changes, verify returned documents, and track updates in recurring reports.

pdf.net currently compares two files at a time, so if you have multiple versions, compare them one pair at a time.

How to Compare Two PDF Files Using pdf.net Tool in 4 Easy Steps

best way to compare two PDF files for differences is by using 

. Our platform allows you to highlight variations and compare document contents in seconds while ensuring accuracy.

If it’s your first time using our PDF file comparison tool, here’s a step-by-step guide you can follow:

First, you need to upload a PDF file to our online PDF compare tool. Since this is cloud-based software, you won’t need to download or set up anything beforehand. 

upload a PDF file to our online PDF compare tool

 button, which will prompt you to upload the second PDF file. 

Once the tool finishes the review process, it will automatically highlight the differences between the two files and generate a comparison report that summarizes these. 

highlight the differences between the two files

5.  Finally, you can export the compared files for easy offline access. While you can only export the file as a PDF by default, you can convert the 

 or any other format using our PDF editor if needed.  

When Do You Need to Compare Two PDF Files?

You may need to compare two PDF files to 

verify document edits and updates, ensure consistency in legal documents, or confirm design changes 

One common reason why you may need to compare two 

verify any edits or updates made to existing documents

, especially when working with a team. While there are other ways to do this, such as by checking the file edit history, this is extremely time-consuming and won’t yield completely accurate results.

With pdf.net, however, you can do more than just compare two PDF files. For example, if you want to suggest changes to the document, you can 

 using our tool to notify your team about the modifications you want to make.

#2. Ensuring Consistency in Contracts or Legal Documents

You may also need to compare two PDF files to 

ensure consistency in the information between copies 

of contracts and other legal documents. Using a PDF comparison tool will preserve 

 by identifying discrepancies between copies that could lead to legal disputes or misunderstandings, so you can 

#3. Comparing Design or Layout Changes in PDF Reports

When presenting PDF reports to clients, it’s 

crucial to have a coherent layout to convey professionalism 

and ensure that the design meets the client’s specifications.

However, it can be difficult to manually identify all the changes between two different versions, especially if the differences are minor. Before converting 

 for your reports, consider using pdf.net to compare two PDF files and highlight the differences in their layout, design, and content.

Upload two versions of any document and see every changed line without printing or scanning.

Compare Two PDF Files in Seconds

Manual PDF Comparison vs. Using a Comparison Tool

Now that you know how to compare two PDF files online using pdf.net, you may be wondering why you should choose this method over manual comparison.

common disadvantages of manually comparing PDF files

. Manual comparisons can take hours since you will have to read and check every line and detail on two PDF files. Comparing documents online, on the other hand, can be completed in seconds with a high level of accuracy.

. Manually comparing documents can also result in a significant error margin. In fact, some studies state that human processing for data entry results in 

 than other methods, so rather than risk having discrepancies in important documents, it’s best to use automated tools like difference checkers for PDF files instead.

. While manual comparisons can be doable if you only want to compare two PDF files, it’s not the best option for a higher number of documents. For instance, if you need to compare over 20 files, doing so manually would take days, so it’s better to use an automated PDF tool.

A comparison tool also creates a clear record of what changed, which matters if you need to show someone else exactly what was edited. Scrolling between two windows doesn't leave that kind of trail behind. Once you've confirmed the differences, you can 

3 Key Benefits of Using pdf.net PDF Comparison Tool

more convenient and efficient way to compare two PDF files

, you can’t go wrong with pdf.net’s PDF comparison tool.

Let’s go over our software’s key benefits below:

With an intuitive interface and a simple process for side-by-side PDF comparisons, 

pdf.net is one of the most user-friendly PDF tools 

on the market. You won’t need to follow a manual or a complicated setup to use our tool; all you have to do is upload your file, initiate the comparison process, and download the compared file at the end.

#2. Cloud-Based Access for On-the-go Comparison

If you need to compare PDF versions on the go, you can simply open the web browser on your phone or laptop and use pdf.net; there’s no need to download any additional software. As a cloud-based application, our 

online PDF editor offers the utmost convenience and functionality 

#3. Highlights Both Text and Design Discrepancies

online editor provides you with a comprehensive PDF layout comparison

, meaning it highlights both text and design discrepancies. This can be extremely useful in design or legal documents, where consistency and accuracy in all document copies are vital.

Manually scanning two PDF files for differences is slow and easy to get wrong once a document runs more than a page or two. A comparison tool does the same job in seconds and catches changes a manual read-through would likely miss.

Whether you're reviewing a contract, checking a returned document, or tracking updates in a recurring report, a quick comparison confirms exactly what changed before you sign, file, or 

#1. Are online PDF comparison tools secure?

pdf.net’s comparison tool, in particular, uses HTTPS encryption 

to keep your files protected. Moreover, we don’t store any of your documents or information to reduce the risk of data leaks completely.

#2. How to compare two PDFs side by side online?

To compare two PDFs side by side online, 

you need pdf.net, the best PDF compare tool on the market

. With its user-friendly design and ease of use, you can quickly and easily highlight differences between two documents and generate a comparison report that summarizes these findings.

#3. Can I compare more than two PDFs at once?

Currently, pdf.net compares two files at a time. If you have multiple versions of the same document, compare them one pair at a time, working from the oldest version to the newest.

No, pdf.net's comparison tool doesn't currently support scanned PDFs, since it relies on text comparison.

How to Compare Two PDF Files with PDF.net Tool: Full Guide

How to Compare Two PDF Files with pdf.net Tool: Full Guide

Learn why you can't open a PDF in Outlook and get 7 quick fixes for blocked attachments, blank previews, and errors on any device.

If you can't open a PDF in Outlook, the cause is usually a broken default reader, a blocked attachment, a corrupted file, or an attachment that's too large for the preview pane to render. Outlook may show a blank window, an attachment error, or simply freeze instead of displaying your document.

This is a common problem when a PDF attachment isn't opening in email, and it almost always has a quick, specific fix. Below, you'll find seven causes behind this issue and a step-by-step solution for each one.

If you can't open a PDF in Outlook, it's usually one of a handful of causes: a broken default PDF reader, blocked attachment security, a corrupted file, or a PDF that's too large.

If Outlook preview PDF isn't working, download the attachment first and open it in a dedicated PDF reader instead of the built-in pane.

An Outlook attachment error often clears up after you update Outlook, your PDF reader, and your antivirus software.

You don't need Adobe Acrobat to open a PDF attachment; a browser-based tool like pdf.net works on desktop, phone, and Android.

If a PDF opens blank in Outlook, the file may be corrupted, or your preview pane may not support it.

7 Causes Why You Can't Open a PDF in Outlook and How to Fix It

You can't open a PDF in Outlook because of a

Here’s a quick overview of the seven most common causes and how to quickly fix them:

Now let’s examine each cause and a specific, tested fix.

#1. Your Default PDF Reader Is Broken or Missing

If your default PDF reader is broken or missing, Outlook may open a blank window, freeze, or show no response when you click a PDF attachment. This 

file association that was never fully registered

 in the system settings, then repair or reinstall it if the issue continues. If you’re using the Windows operating system, follow these steps:

Set a PDF reader for the .pdf extension. 

On the other hand, if you’re using a Mac, right-click the file, select 

If you'd rather skip desktop software entirely, compare a few of the 

 online and pick one that handles attachments consistently.

#2. Outlook Attachment Security Is Blocking Access

Outlook blocks certain file types and flags others as potentially unsafe 

, which is a common reason Outlook won't open attachments. You'll usually see a banner saying access was blocked, even though the file itself is harmless.

If you're on a company account, ask your administrator to allow PDFs from your domain. Keep in mind that Microsoft maintains a 

 you can check against your file. Once the sender is marked safe, the attachment should open normally.

 often opens fine on the sender's end but fails

throws an error the moment you try to view it in Outlook

. This usually happens during upload or if the connection dropped while the file was being sent.

rather than a forward of the same broken copy. If you already have the file elsewhere,

 to confirm whether the problem is the file itself or your Outlook setup.

 is structured helps explain why a partial download or interrupted transfer breaks the file, and a 

 can repair minor structural issues, but severely corrupted PDFs usually need to be replaced or restored from the original source.

, especially ones packed with scanned pages or high-resolution images, can take too long to render in Outlook's preview pane, so the app may time out and show an error instead. This is 

especially common with multi-page scanned documents

Ask the sender to compress the PDF before resending it, or download the file first and open it in a dedicated reader instead of previewing it inside Outlook. 

Compressing a large file can shrink it significantly without a noticeable drop in quality

, which makes it far easier for Outlook and other email clients to handle. Here’s how to do it with 

Upload the file directly from your storage or use the drag-and-drop option instead. 

Choose one of the three compression levels and click 

Choose one of the three compression levels and click Compress and download.

#5. Your Outlook or PDF Software Is Outdated

 behind an Outlook PDF attachment not opening. Older builds of Outlook or your PDF reader may not support newer 

, which can cause attachments to fail silently or display incorrectly.

 to the latest version, then check for updates within your PDF reader as well. On Windows, go to 

 since some changes only take effect after a full restart.

#6. Antivirus or Firewall Settings Are Blocking the File

Security software sometimes quarantines PDF attachments automatically, particularly 

if the sender is unfamiliar or the file was flagged by a scan

. This can make it look like Outlook itself is malfunctioning when the real block is happening at the antivirus level.

Check your antivirus or firewall's quarantine folder

 rather than disabling protection altogether, and only restore a file once you've confirmed the sender and content are legitimate.

#7. You're Opening the Attachment on a Mobile Phone

Attachment previews behave differently on mobile. If a PDF opens blank in Outlook on a mobile phone (iOS or Android), the 

 instead of relying on the in-app preview.

From there, open the PDF in a full mobile PDF app, or an 

 from your phone's browser to view and edit it without installing anything new.

How Do You Open a PDF From Outlook Properly?

 instead of Outlook's built-in preview pane. This single step avoids most rendering, security, and attachment errors.

Double-click the attachment, then select 

If the file still won't open, right-click it and choose 

Click the attachment's dropdown menu and click 

Click the attachment's dropdown menu and click Download

Locate the file in Finder and open it in Preview or another reader. 

Locate the file in Finder and open it in Preview or another reader

If Preview shows an error, try opening the PDF file in Chrome to rule out a corrupted download.

Can You Open Outlook PDF Attachments Without Adobe?

Yes, you can open Outlook PDF attachments without 

On Windows, Microsoft Edge opens PDFs natively, and on Mac, Preview handles most PDFs without any extra installation. Both work fine for simply viewing a document, but they offer limited tools if you need to edit, 

our editor lets you open the attachment directly in your browser

, then edit text, fill out forms, or add a signature without downloading any software. Since we use HTTPS connections, our editor 

, and you can delete your files after processing.

This approach is especially useful if you're on a shared or work computer where you can't install new programs, or if you just want a faster way to handle an attachment than waiting for Adobe Acrobat to launch.

Skip the download-and-install step entirely and work on your PDF attachment right in your browser.

Open, Edit, and Sign PDF Attachments From Outlook Instantly

Best Practices to Prevent Outlook PDF Issues

Most Outlook PDF attachment not opening problems are avoidable with a few habits. The following practices address the causes covered above before they turn into a recurring Outlook attachment error:

Always download attachments before opening them

. Previewing a PDF inside Outlook's reading pane puts extra strain on the app and is one of the most common reasons attachments freeze or fail to load. 

 first and opening it in a PDF reader avoids this entirely, and it also gives you a saved copy in case the original email disappears or gets archived.

. Software updates patch the compatibility issues that cause blank previews and rendering errors in the first place. Set both Outlook and your PDF reader to update automatically if that option is available, and restart the apps after installing updates so the changes take effect.

Scan attachments before opening unfamiliar files

Treat any unexpected PDF, even one that looks legitimate, with some caution before opening it. Save the file, run it through your antivirus software, and confirm the sender is who they claim to be if anything about the message feels off. This habit protects you regardless of which device or email client you're using.

Compress large files before sending or receiving them

. Oversized PDFs are more likely to stall in transit and time out inside Outlook's preview. Before sending a large document, 

 so the recipient's inbox can handle it without delay. If you're on the receiving end, ask senders to do the same, or 

 as a workaround for documents that won't shrink easily.

Most cases where you can't open a PDF attachment in Outlook come down to one of seven fixable causes, and downloading the file before opening it solves a surprising number of them on its own. Keeping your software updated and your antivirus current handles most of what's left.

If you'd rather skip the troubleshooting altogether, pdf.net lets you open, edit, and manage PDF attachments straight from your browser, on any device, without installing Adobe Acrobat or anything else.

#1. How do I change my default PDF reader?

You can change your default PDF reader by going to 

 on Windows, and selecting a new program for the .pdf extension. On a Mac, right-click any PDF file, choose 

#2. Why can I preview PDFs but not open them?

You can preview PDFs but not open them because Outlook's reading pane uses a lightweight viewer that renders simple files without fully opening them. Download the attachment and open it in a dedicated PDF reader instead, since the full file often loads correctly outside the preview pane.

#3. How do I enable the PDF viewer in Outlook?

You can enable the PDF viewer in Outlook by making sure your default PDF reader is installed and set correctly in your system settings, since Outlook relies on that program to display attachments. If PDFs still won't preview, update Outlook and your reader, then restart both applications.

Can't Open PDF in Outlook? 7 Easy Fixes That Work

The reasons why links in a PDF are not working range from broken hyperlinks in the text to blocked security settings of the document.

Links in a PDF are usually not working because the link was not added correctly, the file was converted from another format, the PDF is corrupted, your viewer does not support links, or your security settings are blocking them.

a PDF is a static file, and any hyperlink inside one depends entirely on how it was created, saved, and opened

. A link that works perfectly in the original document can easily stop working the moment the file is converted, resaved, or opened in a different program.

In this guide, we will cover the most common reasons behind broken PDF links and walk you through how to fix each one, including issues specific to Chrome.

Broken links in a PDF are usually caused by incorrect link creation, format conversion, file corruption, unsupported viewers, or restrictive security settings.

Each cause has a specific fix, from re-adding the hyperlink to adjusting your PDF reader's settings.

You can make links clickable in a PDF using a few simple editing steps.

Chrome's built-in PDF viewer is a frequent source of link problems and usually needs a separate fix.

Keeping your PDF viewer and browser updated prevents most future link issues.

 may not be working for a handful of predictable reasons, ranging from how they were created to how the file is opened. Here are the five most common ones and what to do about each one.

#1. The PDF Links Were Not Added Correctly

. For instance, if a link was pasted as plain text instead of a real hyperlink, or if it was added incorrectly during editing, it can look clickable without actually working. This is one of the most common reasons behind PDF links not working, especially in documents built from templates or copied from another file.

Open the PDF in an editor that supports hyperlink editing and check whether the text is a live hyperlink or just formatted to look like one. If it is plain text, recreate the hyperlink and test it before sharing the file again.

#2. The PDF Was Converted From Another Format

 strip out hyperlinks if the original formatting was not preserved

 with an outdated tool, or when a presentation or spreadsheet is exported without its embedded links intact.

Re-export the original file using a converter that preserves hyperlinks, then open the new PDF and click each link to confirm it still works. If links are still missing, add them back manually in your PDF editor.

A corrupted PDF can lose more than just its links. Corruption usually happens 

during an interrupted upload, a failed download, or an error while saving the file

, and it can affect text, images, and clickable elements at the same time.

Check whether other parts of the document look correct and whether there’s any 

 or garbled content. Otherwise, ask the sender for a fresh copy or re-download the original file.

#4. Your PDF Viewer Does Not Support Links

Not every PDF viewer handles interactive elements the same way. Some lightweight or outdated readers only display the page content and ignore embedded hyperlinks, based on how each application implements the 

, which means a perfectly working link can appear broken simply because of the software you are using.

Blog

How to Compare Two PDF Files with pdf.net Tool: Full Guide

Can't Open PDF in Outlook? 7 Easy Fixes That Work

Links in PDF Not Working? 5 Easy Ways to Fix Broken Ones

How to Convert PDF to PowerPoint: Turn Documents Into Slides

How to Convert PDF to Word Without Losing Formatting

How Do I Extract Pages From a PDF: The Easiest Solution

Can't Sign a PDF? 7 Typical Reasons and How to Fix This

How to Upload a PDF To a Google Doc: 3 Easy Methods

Why You Can’t Highlight Text in a PDF: Common Issues and Easy Fixes

Why Is My PDF Printing Blank? 5 Causes and Fast Fixes