Fill PDF form

Fill PDF form handles the five AcroForm field types that hold a user value: text fields, including multi-line ones that get a proper text area, check boxes, radio groups, dropdowns and multi-select option lists. Each one appears in the Form fields panel as a labelled control, using the field's own name as the label, with the field's tooltip shown underneath when the form defines one. Push buttons and signature fields are deliberately skipped, because neither carries text you type — a signature widget needs a cryptographic operation, not a value. If a document contains none of the five fillable types, the panel stays empty and the tool says so plainly rather than offering you a download that would change nothing.

The usual cause is an XFA form, the legacy Adobe LiveCycle format that stores its fields as an XML payload instead of ordinary AcroForm objects. The tool detects that case and shows an amber notice above the panel rather than leaving you guessing. The fix is to open the file in a recent Acrobat Reader and use Print to PDF: the printed copy is a normal PDF whose fields are regular AcroForm widgets, and that copy fills fine here. The other possibility is that the document only looks like a form — a scan, or an export where the boxes and lines are drawn artwork with no interactive layer at all. In that case there is nothing to fill, and you would add text on top with an editing tool instead.

Flattening bakes your values into the page's content stream and removes the interactive layer, so the document reads identically in every viewer and the recipient cannot alter what you entered — the right choice for anything you are submitting. Saving as fillable keeps the widgets live, values and all, so the next person can correct a typo or complete the fields you left blank, which suits a form you are partly filling and passing on. Flattened is the default. The two are easy to tell apart afterwards by filename: a flattened save comes out as yourfile-filled.pdf and a fillable one as yourfile-filled-form.pdf. Flattening cannot be undone, so keep the fillable copy too if you might need to edit again.

Most accented Latin characters — é, ñ, ç, ü, ä and the rest of Latin-1 — are drawn with Helvetica and come out exactly as typed. If a value uses characters Helvetica cannot encode, such as Polish ł, Cyrillic, Greek, Hebrew or Arabic, the whole form switches to an embedded Unicode font before anything is written, and that font is registered in the form's own resources so a viewer that regenerates an appearance later can still resolve it. CJK and emoji are the hard limit: they cannot be drawn, and rather than quietly saving a PDF full of blank boxes the tool names the exact offending character so you can change it. A running banner counts how many of your fields currently hold non-Latin text.

Both rules are read out of the PDF itself and enforced before anything is saved. A field the form marks as required shows "(required)" in its label and blocks the save with a Required message if you leave it empty — an unticked check box counts as empty, and so does an option list with nothing selected. A text field that declares a maximum length shows that limit next to its label, caps typing at it, and is re-checked on save. If anything fails, the offending fields are highlighted and the save is refused with a message pointing at them; editing a field clears its error immediately. Nothing beyond those two rules is validated — the tool will not tell you a date is implausible or a total does not add up.

Nothing you type is transmitted, stored or logged — the values exist only in the browser tab until you save the PDF. The document is read from your disk, the fields are set with pdf-lib in memory, and the finished file is handed to your downloads folder; the page has no server component, so there is nothing anywhere to receive a copy. That is the whole reason to fill a form here rather than on a service that asks you to upload it, because the forms people actually fill are tax returns, medical intake sheets, rental applications and employment paperwork, all of them full of identifiers you would not paste into an unknown website. Closing or reloading the tab discards the values with nothing left behind.