PDF comparison found no text changes: what to check next
GlobePDF ·
“No selectable text differences found” does not establish that two PDFs are identical. If a revised file looks different, or you need to approve it, use the result as one part of your review. Check the versions, corresponding pages, visible content, and document features separately.
1. Read the result as a text check
In GlobePDF’s Compare PDF tool, the automatic summary compares the text it can extract from page 1 with page 1, page 2 with page 2, and so on. It separates that text into sentence-like fragments and checks whether each fragment exists on the other page. It does not decide whether the two documents have the same meaning or appearance.
For example, a revised chart can show different bars while keeping the same title and labels. A text comparison may find no changes. Two image-only scans can also contain different visible words while supplying no selectable text to compare.
Order and repetition need a separate check. If a page contains “Check the valve. Start the pump.” and the revision reverses those sentences, both fragments still exist. Likewise, removing one of two identical sentences can leave the same set of fragments. The summary and report can miss these changes. The side-by-side text highlights use a separate matching method, so they may flag repeated text even when the summary does not.
Text-only and graphical comparison answer different questions. Adobe’s comparison documentation also distinguishes them; its additional matching and reporting features are not a description of GlobePDF’s capabilities.
2. Confirm the two versions and the available text
Keep both source PDFs. Open each one and confirm its content, revision details, and page count; similar filenames alone do not establish that you have different versions. In Compare PDF, put the earlier file under “Select original PDF” and the revision under “Select changed PDF.” This determines which text is described as added or removed.
On a page you expect to differ, select and copy the relevant words in a PDF viewer. For a longer check, use Extract text on each file and compare the exported page sections with the visible originals. Check tables and columns carefully: extracted text may not follow the visual reading order.
If a page is image-only, the text result cannot settle whether its visible words changed. Use visual review, or obtain verified searchable copies if you need a text comparison. W3C’s OCR guidance calls for checking the converted text and reading order. OCR output should not be treated as an unquestioned transcription of the scan. The linked searchability guide explains the next steps without changing your originals.
3. Match content before comparing page numbers
An inserted cover can shift every later page. Suppose the original has two report pages and the revision adds a cover at the front. Original position 1 now corresponds to changed position 2, and original position 2 to changed position 3. The automatic text comparison still pairs equal positions, so it can report many changes that are really mismatched pages.
Make a short page map using headings and content, not just printed page numbers. Count positions from the first page in each file. Check any inserted, removed, or reordered pages separately; do not assume one offset remains valid throughout a long document.
Under “Visual differences,” enter the corresponding positions in “Original page” and “Changed page,” then select “Compare page images.” In the cover example, compare 1 with 2, then 2 with 3. This checks one pair at a time. Those fields do not realign the automatic text summary, its shared “Page” control, or the downloaded report.
4. Treat the downloaded report as a starting point
The downloaded comparison report is a PDF containing text findings. It does not include the visual-difference image. Check its “Original,” “Compared with,” and page-count entries before relying on it, especially if you downloaded several reports.
For each changed page, the report lists fragment counts but shows at most four added fragments and four removed fragments. Each displayed fragment longer than 150 characters is shortened to 147 characters followed by an ellipsis. A fragment’s final clause can therefore be missing from the sample.
For example, if six distinct sentences change on one page, the counts can reflect all six while the samples show only four in each direction. Read the complete source page or extracted text to find the remaining changes. Do not approve a revision solely because the displayed examples look harmless.
5. Use pink marks to locate changes, then inspect the originals
After comparing a corresponding page pair, inspect the pink marks in Visual differences. They indicate preview pixels that differ beyond the tool’s threshold. Use them to locate a chart, stamp, shifted paragraph, or other area that needs closer reading.
This is a reduced-resolution preview with a difference threshold, not a full-resolution inspection. Small or faint changes may be missed. The percentage describes differing preview pixels, not the importance of a change or how completely you have reviewed the document. A changed decimal point can matter more than a large decorative change; a displayed zero is not proof of identity.
If page dimensions differ, the tool aligns the rendered images at the top left. Scaling or alignment can produce extensive marks. Check the original dimensions and corresponding content before interpreting those marks as edits. The tool does not automatically align matching paragraphs or register scanned pages.
Open both source PDFs at a readable size and zoom in where needed. Read amounts, dates, names, labels, fine lines, and sentence order directly. Continue through every corresponding pair relevant to your review, including pages with no text changes, and inspect unmatched pages separately.
6. Check required features and record the review scope
Neither a text summary nor a pixel preview is a complete document audit. In the revised PDF, test the links and form fields you need, inspect comments and attachments when relevant, and use the appropriate viewer checks for accessibility or digital signatures. A signature’s visible mark is not a signature-validation result.
Keep the two source files, the downloaded text report, your page map, and notes about what you inspected. A useful note might say: “Compared original pages 1–2 with revised pages 2–3; reviewed the new cover separately; checked the chart and totals in the originals; links still need review.” This is an example of scope, not a test result.
If a required check remains unresolved, name it before handing off or approving the revision. Describe what you actually checked rather than reducing the outcome to “the PDFs are identical.”