Kiểm tra PDF

Công cụ này làm gì

This reads a document and reports on it rather than changing it. Four passes answer four different questions: is the file structurally sound, is it locked, what does it give away about whoever made it, and can a screen reader read it. Every finding that has a fix names the tool that applies it, so the report is something you can act on instead of a list of things to worry about.

Before sending a document you did not create, or one you did: to see what metadata is riding along, whether there are attachments you had forgotten, whether it is a scan that nobody's screen reader can read, or why another program refuses to open it.

Cách hoạt động

1. Drop the PDF onto this page. Nothing is written back to it - inspection is read-only.
2. Leave all four checks on for a full report, or switch off the ones you do not need.
3. Press Inspect. Three engines are used: qpdf for encryption and structure, pdf-lib for metadata, attachments and links, PDF.js for the text layer.
4. Read the report. Each finding is marked ok, information, warning or danger, and the ones that can be fixed carry a link to the tool that fixes them.
5. Keep the report as a web page, or switch the format to JSON under advanced options if a machine is going to read it.

The structural pass runs qpdf's own check, which walks the cross-reference table and the object streams and reports whatever does not add up. A warning here is usually why some other program refuses to open the file, and Repair PDF is usually the answer. A clean check is a stronger statement than it opened on my machine.

The security pass separates the two kinds of protection people confuse. A document may be encrypted so that it cannot be opened without a password, or encrypted with an empty password so that it opens for everyone and merely declares restrictions. The report says which it is, how many bits the handler uses, and lists the permission lines exactly as qpdf reports them. It does not verify signatures - that is Verify signature's job.

The privacy pass is the one that surprises people. A PDF routinely records who created it, which program produced it, and sometimes the full path of the file on that person's disk; it can carry attachments nobody remembers adding, and links to hosts you might not want to be seen visiting. The report names the identifying fields, lists the attachments, and shows only the hosts of external links.

The accessibility pass is the one almost nobody else runs. It checks whether the document has a text layer at all - five pages sampled evenly across the whole document, because a cover sheet is often the only page with real text in an otherwise scanned file - and whether the document has a title and an outline. Without a text layer the file is a picture of a document.