Fix Adobe Acrobat Compare Reporting False Differences in PDFs
Question details
The user needs to understand why Adobe Acrobat Pro Compare flags numerous false differences, such as incorrect spaces and symbols, between two visually identical PDF documents.
- Product
- Adobe Acrobat Pro
- Device & OS
- not provided
- Scenario
- Using the Acrobat Pro Compare feature to identify revisions or changes between two versions of a PDF document.
- Observed behavior
- The comparison tool incorrectly reports missing spaces, changed symbols, and formatting discrepancies, typically triggered when the documents are created or edited in different applications like Adobe InDesign and Acrobat DC Pro.
Before comparing your documents, check the document properties of both files to verify the source applications used to generate them, as internal structural variations often trigger false positives.
Standardize PDF Creation and Export Processes
Re-export both documents using the exact same application and settings to align their internal text structures and prevent false comparison flags.
Different applications, such as Adobe InDesign and Acrobat Pro, write PDF text structures and encodings differently. Even if the text looks identical visually, the underlying code varies, which the Compare tool detects as a difference.
Open the original source files for both document versions in their native application (e.g., Adobe InDesign or Microsoft Word).
Export both the original and the revised documents using the exact same PDF export preset (such as 'High Quality Print' or 'PDF/X-4').
Ensure neither PDF is edited in a secondary application (like Acrobat DC Pro) before running the comparison, as this can alter the text structure.
Open Acrobat Pro, navigate to the Compare Files tool, and run the comparison on the newly exported, structurally identical PDFs.
Compare Rasterized (Image-Based) Versions
If you cannot standardize the source files, converting the PDFs to image-based files forces the tool to compare visual pixels rather than text code.
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Frequently Asked Questions
Why does Acrobat Compare show differences when there are none visually?
This happens when the internal text structures or character encodings of the PDFs differ. If one PDF was exported from Adobe InDesign and the other was modified in Acrobat DC Pro, the comparison tool flags invisible structural variations, like different space characters or font mappings, as differences.
How can I prevent false differences when comparing PDFs?
To prevent false positives, ensure both PDF documents are generated using the exact same source application and the same export settings. Additionally, avoid making intermediate edits in a third-party PDF editor before running the comparison.
Can embedding different fonts cause false compare results?
Yes. If the two documents use slightly different font versions, or if one embeds the entire font while the other subsets it, the comparison tool might detect the underlying text as different even if it looks identical to the naked eye.
Is there a way to only compare visual differences in PDFs?
Yes, you can rasterize both PDFs by saving them as images (like PNGs) and converting those images back to PDF. Comparing these flattened files forces the tool to ignore hidden text structures and focus solely on visual pixel differences.
