Fill PDF Form

Why a form you can fill in a browser matters

The forms people fill in are the most personal documents they handle: tax and pension forms, visa and passport applications, insurance claims, medical history questionnaires, tenancy and employment paperwork. Most online form fillers work by uploading the PDF to a server and sending back the completed copy, which means your passport number and medical answers spend time on a computer you know nothing about.

This tool reads the form with pdf-lib inside the page, draws it with pdf.js — the engine Firefox uses to show PDFs — and writes your answers into the same fields, all on your own machine. There is nothing to sign up for, no daily limit, and no watermark added to the result.

Fillable forms, flat forms and XFA forms

A PDF can look like a form without being one. A fillable form (the PDF standard calls it an AcroForm) contains real fields: named boxes that know whether they hold text, a tick or a choice from a list. Those are what this tool fills, and every competent PDF reader will show your answers in them afterwards.

A flat form is just a picture of a form — a scanned paper form, or a document designed to be printed and filled with a pen. It has no fields at all, so there is nothing to type into. The tool says so plainly, and the fix is to place your text onto the lines yourself with Add Text to PDF, then sign with Sign PDF if the form asks for a signature.

The third kind is the awkward one. XFA forms use Adobe's own XML Forms Architecture: the fields are not stored in the PDF at all, but generated from an XML template when Adobe Acrobat or Reader opens the file. Every other viewer shows a page saying “please wait” or that the document cannot be displayed. XFA was deprecated in PDF 2.0, but plenty of government and corporate forms still use it. No browser tool can fill a dynamic XFA form, this one included — open it in Adobe Acrobat Reader, which is free, or ask the issuer for a standard PDF. Some forms carry XFA alongside ordinary fields; those are filled normally, and the XFA layer is removed so that every viewer shows what you typed rather than Adobe Reader showing the old values.

Filling on the page, or as a list

On a desktop screen, the form appears as itself, with each field outlined where the form designer put it. Text boxes take typing, multi-line boxes wrap, checkboxes tick, radio buttons pick one option, and dropdowns open their own lists. The positions are worked out from each field's rectangle and the page's rotation, so a form scanned sideways and rotated for viewing still lines up.

Comb fields — the rows of single-character boxes used for postcodes, PAN and passport numbers — accept exactly as many characters as they have boxes, spaced one per box. Fields marked as required are listed if you leave them empty, though you can still save, because only the people receiving the form decide what they will accept.

The list view shows the same fields as ordinary labelled controls, grouped by page and labelled with the field's tooltip, which is the label the form's designer wrote for exactly this purpose. It is the better view on a phone, where a field on a shrunken page is too small to tap, and it is the view to use with a keyboard or a screen reader. Both views edit the same answers, so you can switch at any time.

Characters, fonts and calculated fields

When a value changes, the field's appearance has to be redrawn, and that uses one of the 14 standard PDF fonts — Helvetica, Times or Courier, chosen to match the font the form asks for. Those fonts cover Western European Latin letters, accented ones included, but not Devanagari, Cyrillic, Greek, Chinese or emoji. Rather than crash or silently drop letters, the tool marks the field and says which characters it cannot draw. A few characters have faithful equivalents and are converted automatically: the rupee sign is written as “Rs.”, and curly quotes and dashes are kept.

Fields you do not touch are left exactly as they were, including their original appearance and font. Checkboxes and radio buttons keep the form's own tick, cross or dot.

One honest limit: some forms total columns or check entries with JavaScript built into the PDF. This tool does not run a document's scripts, so a calculated total will not update here. It updates when the form is opened in a reader that runs them, such as Acrobat Reader.

Flatten, or keep it editable

By default the completed form stays fillable: anyone who opens it can still change the answers, which is right when you may need to correct something or someone else must add to it.

Flattening paints your answers into the page and removes the fields. The form then looks identical in every viewer and printer, and the answers can no longer be edited with a form filler. It is the usual choice before emailing a final copy. Keep the unflattened file too, in case you need to change an answer later — flattening cannot be undone.

If the form was digitally signed by its issuer, filling it changes the file and the signature will show as invalid afterwards. That is what a digital signature is for: it proves the bytes have not changed since signing.