How to fill in a PDF form without Acrobat

If a PDF form is fillable, any modern viewer, or the PDF form filler, lets you type into its fields and save the values back into the file. If it is a flat PDF that only looks like a form, you place text on top of the page instead. The first job is working out which kind you have; the rest is mostly about saving the result so it looks the same to the person who receives it.

Fillable or flat?

A fillable form contains interactive fields defined in the PDF's form structure, usually called an AcroForm. In most viewers the fields are highlighted or show a cursor when you click them. A flat form is just a page with lines and boxes, often a scan or a document exported without fields. The quickest test is to drop it into the form filler: it lists every field by name, or tells you the document has none. For a flat form, add text to PDF lets you click anywhere on the page and type real, selectable text.

The field types

• Text fields, single-line or multi-line;
• Checkboxes, ticked or not;
• Radio buttons, where choosing one option clears the others in its group;
• Dropdowns and list boxes, some allowing several choices;
• Signature fields, reserved spaces for a signature;
• Buttons that run actions such as printing or submitting.

Field names are set by whoever made the form, so some are clear (Surname) and some are not (Text12). When names are cryptic, keep the original open in a viewer beside the filler to see which box is which.

Filling and saving

The form filler shows each field with its current value: text boxes for text, a checkbox for ticks, and lists for radio, dropdown and list fields. Fill them in and save. The values are written back into the real fields, so the result is still a filled form that other software can read, and each field's appearance is regenerated so viewers that do not draw values themselves still show them. If a field cannot be set, usually because of an unusual font, the save message says how many. The whole job runs on your device, which matters for tax forms and applications full of personal details.

The filler cannot open a password-protected PDF; that includes forms locked only against changes, which open normally in a viewer but are still encrypted. In that case, use a full PDF viewer such as Adobe Acrobat Reader, or ask the sender for an unlocked copy.

XFA forms and the please-wait page

Some forms, often from governments and large organisations, use XFA, Adobe's XML Forms Architecture, introduced with PDF 1.5. A dynamic XFA form builds its pages when it opens, so in a viewer that does not support XFA you see only a single page saying, in effect, please wait and try Adobe Reader. XFA was deprecated in PDF 2.0, and support outside Adobe's own software is limited. My form filler, like the pdf-lib library it is built on, does not read XFA: on a hybrid form that also contains ordinary fields it removes the XFA data and fills those fields, and on a pure dynamic XFA form it finds no fields. For those, Adobe Acrobat Reader is the practical option, or ask whether an ordinary PDF version exists.

Flattening, signing and sending

Before sending, decide whether the recipient needs to process the fields or just read them. Ticking flatten as you save bakes the values into the page so they cannot be changed and display the same everywhere; What flattening a PDF does, and when you should do it explains the trade-offs, and the flatten tool does it to a form you have already filled. Signature fields are left for the sign tool, which places a drawn signature on the page. That is the digital version of print, sign and scan, not a certificate-based digital signature; Electronic vs digital signatures: what each is, and what a drawn signature on a PDF proves explains when the difference matters. Check the final file in a second viewer before you send it.