Making a Flat PDF Fillable: Add Text Boxes, Check Boxes and Radio Buttons

You have a form as a PDF. It has lines to write on and little squares to tick, and the cursor will not go into any of them. The usual advice is to print it, fill it in by hand and scan it again. There is a better way: put real fields on top of the page, so anyone can type into it on a screen.

Flat versus fillable

A fillable PDF carries form fields: named boxes that a reader knows how to fill in. A flat PDF only looks like a form. Scans are flat by nature, since they are pictures of paper. Many exports from word processors are flat too, because the boxes were drawn as lines or table borders. The quick test is to open the file and click a box. If nothing highlights, it is flat. Flat is the normal state: in 9,511 real PDFs we checked, only 140 had form fields at all. The Fill PDF Form tool says so too, and will not open a flat file for typing. If your file is a scan with no text at all, scanned versus text PDFs explains what that means for the rest of what you can do with it.

Adding the fields

Drop the file into the Create Form tool. Choose a field type, then drag on the page to draw its box over the printed line or square. A plain click drops a standard-size box instead. Each field has a name, which must be different from every other name, and the tool tells you which one clashes rather than renaming it behind your back.

• Text boxes can be multiline, have a maximum length, and use a set font size or fit their own.
• Checkboxes are for yes-or-no answers, one box each.
• Radio buttons are for pick-one answers. Every button in a group shares the group name and has its own value, such as Small, Medium and Large. Choosing one clears the others. Values use plain letters, digits and punctuation, without accents.

Give each field some hint text, a few words saying what it is for. It is read out by screen readers and shown as a tooltip, and without it someone using one hears only "edit text" for every box on the page. You can also mark a field required, or read-only if it holds something the person filling in should not change.

Checking that it works

Download the copy, then open it in the Fill PDF Form tool and type into every box. Tick the check boxes. Choose each radio button and make sure only one stays chosen. Then open it once in a different reader, because the people you send it to will not all use the one you tested in. The checklist for checking a PDF before you send it covers the rest of what a finished file can still carry.

What these fields do not do

They hold what is typed and nothing more. There is no scripting, so a field cannot add up a total, format a date or refuse a bad answer, and the tool does not make drop-down lists. Text is limited to Latin characters. If the PDF already has some fields they are kept as they are and yours are added alongside; a form that also carries an Adobe XFA packet has that packet removed so Adobe Reader shows the fields you see. A form made only of XFA cannot be opened here at all.

Do this last

Merging, reordering and splitting keep a field's box on the page but not the field, so the result looks like a form and is no longer fillable. Finish the document first, then add the fields as the last step. Once someone has filled it in, the flatten tool can lock the answers into the page; what flattening does explains when that is the right choice and when it is not. Saving any change to a digitally signed PDF invalidates its signature, so add fields before it is signed, not after.

Everything here runs in your browser. The file is read and rewritten on your device, and nothing is sent to a server.