How to compare two PDFs
- Upload exactly two PDFs
The first is treated as the original and the second as the revision.
- Compare
You get a plain-text report.
- Read the report
Lines beginning with a minus were removed; lines beginning with a plus were added. Pages with no differences are counted but not listed.
Why this matters for exam and study documents
Specifications get revised quietly. Comparing the 2023 syllabus against the 2025 one tells you exactly which topics were added and which were dropped - a question no summary page answers reliably.
What is kept, what changes, and what this will not do
These change how a document presents itself rather than what it contains - with one important exception, which is that cropping hides content without removing it.
Kept
- Both source files, which are never modified
Changed
- Nothing. This tool produces a report and does not alter either document.
Limits
- Text only. Layout changes, moved images and colour changes are invisible to it.
- Pages are compared by position, so inserting a page early on reports every subsequent page as changed.
- Scanned documents have no text layer and cannot be compared.
Questions and answers
Why is every page reported as different?
Almost certainly because a page was inserted or removed, which shifts everything after it. Align the documents first by extracting the comparable range from each.
Can it compare scanned documents?
No. There is no text to compare. Two scans of the same page are different photographs even when the page is identical.
Does it show me the differences visually?
No, it produces a text report. A visual overlay sounds better than it reads in practice, because the moment text reflows every subsequent line appears to have moved.