Checked against the current Windows build. Where an article names a menu, a button or a message, that is the wording in the application, not a paraphrase.
Six things that travel and never appear on a page
Metadata: title, author, subject, keywords, creator, producer, and the created and modified dates. The creator field routinely names the application, and sometimes the machine, a document came off.
Attachments: whole files carried inside the PDF. One real filing turned up here carrying nine of them — an objects clause, a utility bill, a no-objection certificate — 940 KB that nothing on any page mentioned.
Content outside the crop box, which cropping hid and did not delete. Form field values, including ones whose boxes sit outside the visible area. Annotations, which carry an author name and note text along with their position. And, in a file signed more than once, the earlier revision that the countersignature had to preserve.
None of it is exotic. It is the ordinary contents of an ordinary PDF, and the reason it surprises people is that no reader puts it on screen.
One command each, and three panels in the window
creasepoint info-meta file.pdf prints all eight metadata fields, with (none) where one is empty. creasepoint attachments file.pdf lists what is embedded, numbered from one. creasepoint annotations file.pdf gives the page, the type, the box, the author where there is one, and the note text. creasepoint fields file.pdf describes the form, and adding --signatures lists the signature fields by name and says which are still empty.
Then the two that read the page itself. creasepoint objects file.pdf --page 1 lists every object with its text and its bounding box, and creasepoint find file.pdf --query 4412 searches for a value you are worried about, on every page at once. Inside the window, the Edit tab carries Properties, Attachments and Bookmarks, which cover the first three of those without a terminal.
An earlier revision is a real thing, and one command writes it out
Most operations rebuild the document and write a single revision. Signing into an existing field and countersigning are the exceptions: they append, because appending is the only way to leave an earlier signature still covering the bytes it signed. The command line prints a revisions line after any operation that writes, and it says either one, with no previous content retained, or that there is more than one.
When there is more than one, creasepoint signed-version file.pdf --signature 1 --out earlier.pdf writes the document out exactly as it stood when that signature was made — the original bytes truncated at the signed length, not re-saved, because re-saving them would stop them being the bytes that were signed. If you signed a draft, corrected it, countersigned and sent it on, that one command hands anybody the draft.
What comes out, and what does not
Metadata comes out. creasepoint set-meta file.pdf --title "" --author "" --out clean.pdf clears the fields you name and leaves the ones you do not name alone. Creator and producer are shown by info-meta and are not among the four that command sets.
Attachments come out: creasepoint attachments file.pdf --remove 2 --out clean.pdf, using the numbers from the listing. Whole pages come out, because delete and extract build a new document rather than appending to the old one.
Cropped-away content does not come out, and cropping harder does not help. Annotations can be listed but no command removes one. And a watermark, a page number or a header is written into the page's content as an object, so from then on it is part of the page: taking one off means deleting that object, not pressing an undo button on a different day.
The one that is not in any listing
We collect no telemetry, and there is nothing in this application that sends a document anywhere. Windows is a separate matter. If the process reading your PDF crashes, Windows Error Reporting sends diagnostics to Microsoft, and those can include data from the document that was open at the time. It goes to Microsoft and never to us, it is not ours to switch off, and that is why it is written here rather than left for you to find. The privacy page puts it first for the same reason.
Worth saying alongside it: a separate cloud product is planned under the same name. It does not exist yet, and it will never be a feature inside this application. Using that one, if it ships, would mean uploading on purpose.
The two places worth looking next.
Read the matching guide if you want the reasoning rather than the fix, and check limitations before spending any longer on it — some of what people look for here is absent on purpose.