Fix Acrobat Compare Files Not Detecting Differences in Scanned PDFs
Question details
Adobe Acrobat's Compare Files tool fails to highlight differences in scanned documents, such as altered dates or missing data in laboratory reports.
- Product
- Adobe Acrobat DC
- Device & OS
- not provided
- Scenario
- Comparing two scanned or image-based PDF documents to find visual or text alterations.
- Observed behavior
- Acrobat reports that there are no differences between the two scanned files, even though physical changes exist and are detectable by other comparison tools.
Ensure both PDF files are clear and fully legible. If the scanned documents are of very low resolution, consider running OCR (Optical Character Recognition) first to convert them into searchable text for better comparison accuracy.
Change Comparison Mode to Scan/Drawing/Picture
Adjusting the document comparison settings allows Acrobat to properly process and compare image-based or scanned PDFs instead of looking for text layer differences.
By default, Acrobat's 'Auto' mode prioritizes text-based comparison. When dealing with scanned documents, the software treats the pages as flat images. This requires a specific comparison mode to detect pixel-level or structural differences.
Launch Adobe Acrobat DC, navigate to the 'Tools' menu at the top, and select 'Compare Files'.
Choose the older file and the newer file you want to compare by selecting them from your local drive.
Click the 'Settings' gear icon located in the Compare Files dialog box before initiating the scan.
Under the comparison settings, change the document type mode from 'Auto' to 'Scan/Drawing/Picture', then click 'OK' to save.
Click 'Compare' to run the tool again. Acrobat will now analyze the scanned images structurally and accurately highlight the differences.
Compare PDF Files Easily with WPS Office
If you need a reliable way to manage and compare your documents, WPS Office offers a highly capable PDF toolkit. With its lightweight design and built-in document tools, you can easily handle scanned documents, run OCR, and compare files with precision.
- 1. Open WPS Office: Launch WPS Office on your computer and select the 'PDF' tab from the home screen.
- 2. Access PDF Tools: Navigate to the 'Tools' tab to explore various PDF management features, including OCR and document editing.
- 3. Process Scanned Documents: Use the 'OCR' feature to turn your scanned image-based PDFs into searchable, editable text files for easier comparison.
- 4. Review and Manage: Utilize the 'Comment' and 'Review' tools to highlight and track the differences between your documents visually.
Frequently Asked Questions
Why does 'Auto' mode fail to detect changes in scanned PDFs?
The 'Auto' mode in Adobe Acrobat primarily looks for differences in the underlying text layers of a document. Scanned PDFs are essentially flat images without a text layer, so 'Auto' mode sees no text to compare. Switching to 'Scan/Drawing/Picture' forces the software to compare the visual pixels.
Can I compare PDFs if only one of them is scanned?
Yes, but it is highly recommended to run OCR (Optical Character Recognition) on the scanned document first to convert it into a text-searchable PDF. This allows for a more accurate comparison against the other text-based PDF.
Does the Compare Files feature work on password-protected PDFs?
You can only compare protected files if you have the appropriate passwords to unlock both documents. You will be prompted to enter the passwords before the comparison tool can process and display the differences.
