You opened the PDF to make a small change. Every tool is greyed out. Or you can click in but typing does nothing. The file is sitting there refusing to be edited.
Three things stop a PDF from editing. Each has its own fix.
What's actually going wrong
Permission password. The file has owner-level encryption that blocks edits even though it opens normally. Scanned image. The 'text' you're trying to edit is a picture; there's nothing to type into. Signed file. The PDF carries a signature, and editing would invalidate it, so the viewer blocks changes.
Look at the title bar — if it says 'Secured' or 'Protected', you've got permission encryption. If selecting text doesn't highlight anything, you've got a scan. If there's a signature bar at the top, you've got a signed file.
The quick fix
Open the PDF in Flint's editor. If it's permission-locked but you own the password, unlock the PDF first — Flint then treats it as a regular file. If it's a scan, the editor offers an OCR option that builds a real text layer you can then edit.
For signed PDFs, the signature has to be removed or invalidated to edit. Make a copy, edit the copy, re-sign at the end.
If that didn't work
If you don't have the permission password, you can't legitimately edit the file. Ask the sender for an editable version or for the password.
If OCR produces patchy results because the scan is low-resolution, rescan at 300dpi if you have the original. Otherwise, convert PDF to Word and clean up the recognised text in Word, then export back.
Prevent it next time
When sending PDFs for editing, send unprotected versions. When receiving important files, ask for the source format alongside the PDF. And keep an editable master copy of any document you produce — never let the PDF be your only version.
FAQ
Why are all the edit tools greyed out?
Permission encryption is active or the file is marked read-only. Check the document properties or title bar — a 'Secured' indicator confirms encryption. Use Flint to unlock if you have the password.
Can I edit a scanned PDF?
Yes, but only after OCR. Run the file through Flint's converter to add a text layer; then edits become possible because there's real text to modify.
Why does editing my PDF invalidate the signature?
Signatures cryptographically commit to the file's exact contents. Any change breaks that commitment, so signed PDFs block edits to protect signature integrity.
Can I bypass a permission password?
Only if you legitimately own the file and have the password. Flint won't crack passwords you don't have — that's bypassing security rather than removing your own protection.
Most uneditable PDFs become editable in Flint's editor once you identify the blocker. Unlock, OCR, or copy — pick the right route and edit.