Compare Two PDFs in Adobe Acrobat: Settings & Results

This guide shows you how to use Adobe Acrobat’s built-in Compare Files tool to spot differences between two PDF versions. You’ll learn how to adjust the comparison settings (like ignoring whitespace or comments) and how to interpret the results, including the summary report and the visual highlights. No prior experience with Acrobat is needed, but you’ll need the desktop version of Adobe Acrobat (Pro or Standard) installed—the free web viewer doesn’t include this feature.

What You’ll Need

• Adobe Acrobat Pro or Standard (desktop app, not the browser extension).
• The two PDF files you want to compare, saved on your computer.
• Basic familiarity with opening files in Acrobat.

Step-by-Step

1. Open the Compare tool. Launch Adobe Acrobat and go to the Tools tab in the top menu. In the search bar, type “Compare Files” and select it from the results. Alternatively, you can use the shortcut Ctrl+Shift+F (Windows) or Cmd+Shift+F (Mac).
2. Select the two files. The Compare Files dialog opens. Under Select the documents to compare, click the folder icon next to Old File (or Original) and choose the earlier version. Then click the folder icon next to New File (or Revised) and choose the updated version. You can also drag and drop files into the fields.
3. Open the comparison settings. Before running the comparison, click the Settings (or gear) icon in the upper-right corner of the dialog. This opens the Compare Settings panel where you control what gets compared.
4. Adjust the comparison type. Under Comparison Type, choose Detailed for a thorough analysis of text, fonts, and layout, or Page-by-Page for a quicker check that only flags whole-page differences. For most uses, Detailed is best.
5. Configure the options. In the settings, you’ll see checkboxes for Ignore options. Check or uncheck these based on your needs:
   • Ignore document structure – ignores changes in tags and bookmarks.
   • Ignore comments – skips annotations and sticky notes.
   • Ignore formatting – ignores font changes, spacing, and alignment.
   • Ignore headers and footers – ignores text in the top and bottom margins.
   • Ignore line art – ignores vector graphics and shapes.
   • Ignore page size – ignores differences in page dimensions.
   • Ignore whitespace – ignores extra spaces, tabs, and blank lines.
   • Ignore text case – ignores uppercase/lowercase differences.
   • Ignore text color – ignores changes in text color.

   For a strict content comparison, leave most unchecked. For a quick review, check the ones that aren’t relevant to you.

6. Run the comparison. Click OK to save the settings, then click Compare in the main dialog. Acrobat processes the files and opens a new window with the results.
7. Read the summary. The results window shows a summary panel on the left. It lists the number of page differences, the count of changes (insertions, deletions, replacements), and a list of pages with differences. Click any page number to jump to that page.
8. Interpret the visual highlights. The main view shows the two PDFs side by side (or overlaid, depending on your view settings). Differences are highlighted with colored boxes:
   • Red – deleted text or content that’s only in the old file.
   • Green – inserted text or content that’s only in the new file.
   • Yellow – replaced or modified content.

   Hover over a highlight to see a tooltip with the exact text change.

9. Use the results panel. At the top of the results window, you’ll see a toolbar with options. Click Next and Previous to cycle through each difference. The Summary button toggles the summary panel. You can also export the results as a PDF or a text file using the File menu.
10. Adjust view if needed. If the side-by-side view is confusing, click the View menu and choose Overlay to see the documents stacked on top of each other, with differences highlighted. You can also change the zoom level.

Common Mistakes

• Forgetting to adjust settings. Running the comparison with default settings may flag trivial differences (like extra spaces) that clutter the results. Always review the settings first.
• Confusing old and new files. If you swap the files, the red/green highlights will be reversed, making it look like content was added when it was actually removed. Double-check which file is which.
• Using the free web viewer. The online Acrobat viewer doesn’t have the Compare Files tool. You need the desktop app.
• Ignoring the summary. The visual highlights can be overwhelming. The summary panel gives a quick count of changes, which is often all you need.

Tips

• Save your settings. If you frequently compare similar files, set the options once and click Save Settings (in the settings panel) to reuse them next time.
• Use the “Ignore” options wisely. For legal documents, you might want to ignore formatting but not text. For code files, ignore whitespace to avoid noise.
• Export the results. If you need to share the comparison, go to File > Save As to save the results as a PDF, which includes the highlights and summary.
• Compare multiple versions. You can run the comparison multiple times with different “old” files to track changes over time.

Troubleshooting

• “Compare Files” not found. If you don’t see the tool in the Tools tab, click Add next to the search bar and search for “Compare Files” to add it to your toolbar.
• Files are password-protected. If either PDF has a password, you’ll be prompted to enter it. If you don’t have the password, you can’t compare the file.
• Comparison takes too long. For very large files, the comparison can be slow. Try using Page-by-Page comparison type to speed it up, or split the files into smaller sections.
• No differences shown but you know there are changes. This usually means the “Ignore” options are too broad. Go back to settings and uncheck options like Ignore formatting or Ignore whitespace.
• Results window is blank. Close Acrobat and reopen, then try again. If the problem persists, check that both files are valid PDFs (not corrupted) and that you have the latest version of Acrobat.

Frequently Asked Questions

Can I compare scanned PDFs?

Yes, but Acrobat will compare the images. If the text is not OCR’d, it will show as image changes, not text changes. For text-level comparison, run OCR first via Tools > Scan & OCR.

Does the Compare tool work on PDFs with forms?

Yes, it compares the form fields’ positions and values. However, it may not flag changes in JavaScript actions. For those, you’d need to inspect the form manually.

Can I compare more than two PDFs at once?

No, the Compare tool only compares two files at a time. To compare multiple versions, run the comparison sequentially.

How do I get the results as a text list of changes?

After the comparison, go to File > Export and choose Text to save a plain-text summary of the differences.

Is there a way to ignore changes in page numbers?

Yes, check the Ignore headers and footers option in settings. This will ignore any text in the top and bottom margins, which often includes page numbers.

Why does the comparison show a difference when the text looks the same?

This can happen if the font, spacing, or text color differs, even if the characters are identical. Uncheck Ignore formatting to see these subtle differences, or check it to hide them.

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