Signing and security tools

In the tool picker, these tools sit under Signing, Document Security, Verification and Removal.

Signing#

Sign - draw, type or upload a signature and place it on the page. See Sign.
Sign with Certificate - add a digital signature that proves who signed and shows if the file is changed later. See Certificate signing.
Timestamp PDF - add a trusted RFC 3161 timestamp that proves the PDF existed at a point in time. See Timestamping PDFs.

Add Password - set a User Password (needed to open the file) and an Owner Password (controls what people can do once it's open).
Change Permissions - allow or block printing, copying, editing, form filling and other actions.
Add Watermark - stamp text or an image across the pages.
Add Stamp to PDF - add a text or image stamp at a set position. See Content and editing.
Sanitize - remove JavaScript, embedded files, links, metadata and fonts.
Flatten - merge form fields and other interactive elements into the page so they can't be edited.
Unlock PDF Forms - make read-only form fields editable again.

Validate PDF Signature - check who signed, whether their certificate is trusted and whether the file changed after signing. See Validating signatures.
Get ALL Info on PDF - show the PDF version, fonts, page sizes, permissions, metadata and more, as tables or JSON.

Remove Password - unlock a protected PDF. You need the current password.
Remove Certificate Sign - strip digital signatures, for example so you can edit a signed file.

To black out text or areas for good, use Redact.