A 'flat' PDF is one where the content is locked — text and form fields are baked into the page like an image. An 'editable' PDF still has form fields, comments and selectable text.
Here is when you want each.
Flat PDF
Cannot be changed by the recipient. Form fields filled but locked. Comments embedded but unmovable. The file you send when the document is final and you do not want it touched. Common output of sign-pdf — once signed, flat.
Editable PDF
Form fields stay fillable. Recipient can keep editing comments. Useful for documents that should be continued — intake forms, surveys, drafts.
How to switch
Edit-pdf and use 'flatten' to bake everything into a flat PDF. Reverse — making a flat PDF editable again — is harder; usually you need to re-create the form fields.
Best for…
Flat for finalised, signed and shipped documents. Editable for active forms and ongoing edits.
FAQ
Should I flatten before sending?
If the document is final and signatures are placed, yes. Flat prevents accidental edits.
Will a flat PDF still display correctly?
Yes — flatten preserves the visual exactly.
Is flat the same as locked?
Related but not identical. Flat removes editability; password lock prevents opening or editing depending on permissions.
Finalise by flattening in Flint. Send confidently.