Compare two PDFs and see what changed between them. The tool extracts the text from both documents and highlights additions, deletions and modifications. This is the practical way to check what actually moved between two revisions of a contract or specification when nobody kept track of the edits.
The comparison works on text. A change of font, colour or image will not be reported, so it answers "what words changed", not "what does the page look like now".
Only after running OCR on both. Even then, differences in recognition between the two scans can show up as text changes that are not really there.
That usually means the text extracted in a different order from the two files - a re-flowed or re-exported document can produce a very different underlying text order even when the pages look identical.
Files are uploaded over an encrypted connection and processed on CoonTool's own server, not in your browser. The working copy is deleted automatically once the job is done, and in any case within 24 hours. Nothing is stored permanently and no account is required.