How to Fix Acrobat PDF Comparison Missing Document Changes
Question details
Adobe Acrobat DC fails to detect differences between two PDFs, missing changes that older software versions successfully identify.
- Product
- Adobe Acrobat DC
- Device & OS
- not provided
- Scenario
- Comparing two PDF files to generate a difference report, especially when the source documents are scanned or image-based.
- Observed behavior
- The PDF comparison tool produces inconsistent results and skips visual or text changes, failing to highlight the differences in the comparison report.
Determine whether your source PDF files are text-based or scanned image-based documents, as this dictates which comparison settings you should apply.
Change Comparison Mode to Scanned Documents
Manually select the scanned documents setting to force Acrobat to perform a visual comparison instead of just checking the text layers.
By default, Adobe Acrobat DC attempts to automatically identify the document type during a comparison. However, it frequently misidentifies scanned or image-based PDFs. When this happens, the comparison engine misses pixel-level changes. Adjusting the comparison mode ensures accurate detection.
Launch Adobe Acrobat DC, go to the 'Tools' tab, and select 'Compare Files'.
Click 'Select File' for both the Old File and the New File fields to load the documents you want to compare.
Before clicking compare, click on the gear icon (Settings) located at the top right of the comparison window.
Under the 'Document Description' dropdown menu, change the selection to 'Scanned Documents'.
Click 'OK' to save the settings, then click the 'Compare' button to generate an accurate difference report.
Update Adobe Acrobat DC
Install the latest patches to resolve known bugs in the comparison engine.
Compare PDF Files Accurately with WPS Office
If you continue experiencing issues with missed document changes, use WPS Office's built-in PDF tools. It offers an intuitive side-by-side view, making it easy to spot visual and textual differences without navigating confusing engine settings.
- 1. Open WPS Office: Launch WPS Office and open your primary PDF file in the PDF viewer.
- 2. Enable Side-by-Side View: Navigate to the 'View' tab on the top ribbon and click on the 'View Side by Side' option.
- 3. Load the Second PDF: Select the second PDF document you wish to compare from your local directories.
- 4. Synchronize Scrolling: Turn on synchronous scrolling from the view menu to scroll through both documents simultaneously.
- 5. Review and Mark Changes: Visually inspect the documents and use the Highlight or Comment tools to mark differences directly on the file.
Frequently Asked Questions
Can Adobe Acrobat automatically identify scanned PDFs for comparison?
While Acrobat DC has an automatic detection feature, it does not reliably identify every scanned or image-based document. For complex or heavily formatted scans, you must manually select 'Scanned Documents' in the comparison settings to ensure accuracy.
Why do older versions of Acrobat detect changes that Acrobat DC misses?
Acrobat DC introduced a newer, faster comparison engine optimized for modern, text-based documents. However, this updated engine can occasionally skip visual changes in image-based documents if the correct comparison mode is not manually enforced.
Is it possible to compare a text-based PDF with a scanned PDF?
Comparing a pure text PDF with a scanned PDF often leads to inaccuracies. It is highly recommended to perform OCR (Optical Character Recognition) on the scanned PDF first so both documents contain searchable text layers before running the comparison.
