PDF Form Filler

A form with no fields. Most forms that arrive by email are a picture of a form: designed for printing, or scanned from paper. Nothing in the file marks out where the boxes are, so there is nothing to fill. That is what Fill & sign is for.

XFA forms. A different and largely abandoned technology, still used by some government and banking forms, which stores the form as an XML description rather than as PDF fields. Only Adobe's own reader displays them properly, and no browser tool can fill them. If a file opens with "please wait, if this message is not eventually replaced", that is what it is.

Encrypted or password-protected files. These are refused rather than guessed at.

Signature fields. A digital signature is a cryptographic operation tied to a certificate, not a value to be typed. This leaves those fields alone. The site has a separate tool for signing and verifying, and Fill & sign will draw a handwritten-style signature if that is what the form wants.

Read-only fields. Some fields are marked fixed by whoever built the form — a reference number, a total the document calculates. Those are shown but not editable, because overwriting them would be a change the form did not intend to allow.

PDF field values are drawn with a font, and unless a form embeds one, the fonts available are the fourteen standard ones every reader is guaranteed to have. Those cover WinAnsi: English, the western European accented letters, the curly quotes and dashes that word processors produce, the euro sign.

They do not cover Greek, Cyrillic, Chinese, Japanese, Korean, Arabic, Hebrew or emoji. Rather than let the save fail partway through with an exception, the characters are named before you get that far. Where a form genuinely needs them, it has to embed a font that has them, which is a decision made when the form was built rather than when it is filled.

Keeping it editable leaves the form intact with your values in it. The recipient can correct something, which is what you want while a document is still going back and forth. The cost is that different readers draw form fields slightly differently, so it will not look identical everywhere.

Flattening draws the values into the page and removes the form. It looks the same in every reader and nobody can alter it — including you, which is why it is worth keeping the original. This is usually what you want for a final copy.

Neither is a security measure. Flattening prevents casual editing; it is not protection, and it does not remove anything else the file carries. For that, see the metadata inspector and redaction.