Fill PDF

Fill PDF has two modes, and the first one matters more than its name suggests. List the fields in this form opens the document with pdf-lib, walks the AcroForm and returns a table of every field it holds: the name the document uses internally, the type (text, checkbox, radio, dropdown, list, button or signature), whatever value is stored in it now, and for anything with a fixed set of choices, the exact option strings. Those internal names are what the other mode keys on, and they are frequently nothing like the labels printed beside the boxes.

Fill the fields from JSON takes a JSON object whose keys are those names. A string is written into a text field, or picks an entry in a dropdown, radio group or list box, and anything that is not already text is converted before it is written, so 42 arrives as its digits. A checkbox is ticked by true, by the string "true", by the number 1 or by "on", and cleared by everything else — the string "1" included, which is the one that catches people out. A key that matches no field is skipped and counted in the summary as a name not found; switch on Fail if a field name is not in the form and the run stops instead, quoting the names it could not match. Push buttons and signature fields accept no value, so a key pointed at one is reported the same way as a typo.

Flatten the form after filling is enabled by default, and it is blunter than the wording suggests: the values are stamped into the page and every interactive field in the document goes, the ones you never named as well as the ones you filled. The file comes back under its own name with -filled added, so tax-return.pdf becomes tax-return-filled.pdf. Clear the checkbox when the next person still has to type into it, or when you want to open the result and check it before committing. Several PDFs can be queued in one run and the same object is applied to each, with one output file per document; unless the strict setting is on an unmatched name never stops the run, and the summary counts each such name once however many of the documents were missing it.

The work is done in this browser tab and no copy of the document goes anywhere, which is the point when the form you are completing carries a passport number or a salary. The limits are worth reading before you rely on it. Radio groups and list boxes refuse an option the document does not define, but a dropdown does not: pdf-lib stores whatever string it is handed and leaves the option list untouched, so a misspelt choice is written in as a value the form never offered rather than reported back to you. Values are redrawn with pdf-lib's built-in Helvetica when the file is saved, so a field styled in another typeface changes appearance, and a character outside the WinAnsi set — most non-Latin scripts — ends the run with an encoding error rather than filling quietly. Nothing here executes the document's own form JavaScript, so calculated totals and validation rules never fire and what you supply is written verbatim. A scanned form is a picture of a form with no fields in it and is refused; a password-protected file cannot be read until Unlock PDF has removed the password; and a dynamic XFA form keeps its answers in an XML packet that pdf-lib does not write, so what Acrobat shows may not match what you set here.

Runs on your device. Your file is processed directly in this browser.