How to fill and sign a PDF form on a Mac

To fill and sign a PDF form on a Mac, open it in Better PDF, press S for Fill & Sign, and type into the fields, or click anywhere on a flat scanned form and type. Drag a rectangle where the signature goes, draw, type or pick a certificate, and save the signed copy. All of it is free.

The details depend on which kind of form you have, so start there.

What kind of form do you have?

There are two kinds of PDF form, and they look identical until you click.

Forms with fields (often called AcroForms, after the part of the PDF format that defines them) have real boxes built into the file. Click one and a cursor appears. Tab moves to the next. Checkboxes tick, drop-down menus drop down. Government forms, bank forms and anything made in a form designer usually work like this.

Flat forms are pictures of a form, or a PDF exported from a document that was never given fields. The boxes are just printed lines. Clicking does nothing, or selects the whole page. Anything that was scanned is flat.

A quick way to tell: open the form and press Tab. If a box highlights, it has fields.

How do you fill a form that has fields?

The viewer that comes with your Mac handles these, and if that is all you need, use it. Click a field, type, press Tab for the next.

In Better PDF, fields fill the same way. Press S for Fill & Sign and a progress bar counts the fields you have filled and the required ones still empty, so on a twelve-page form you can see that one is missing before you send it. Tab and Shift-Tab move through the fields.

Text fields keep the font and size the form’s author set. Checkboxes, radio buttons and choice lists work as you would expect. If the form has calculation scripts, such as totals that add themselves up, check the totals by eye; not every app runs those scripts the same way.

How do you fill a flat or scanned form?

This is where most free tools get slow. Typically you add a text box, drag it into place and resize it, once per answer. It works. On a long form it takes a while.

In Better PDF, press S and click where the answer should go. A cursor appears at that point and you type. Click the next line and type again. Nothing is drawn over the printed text, and each answer stays movable and editable, so if a line is a little high you can nudge it after. The Fill & Sign palette also has a checkbox and a date tool for the boxes and date lines on a flat form.

A few things that help:

• Zoom in (⌘+) on dense forms so your clicks land on the line, not beside it.
• Hold Space to pan without leaving Fill & Sign.
• If the scan is crooked, your typed text is not. That is normal and nobody minds.

How do you place a signature?

Many apps drop a signature in the middle of the page at a default size and leave you to drag it to the right line. Better PDF works the other way round: you mark the place first.

1. In Fill & Sign, drag a rectangle over the signature line, about the size the signature should be.
2. In the inspector, choose how to sign: draw your name with the trackpad, type it, or pick a certificate, smart card or USB token.
3. The signature is fitted into the rectangle. Move or resize it afterwards if you need to. Esc cancels.

A drawn or typed signature is a picture of your name, and for most everyday forms that is what is expected. If the form asks for a digital signature, a DSC or a qualified signature, it means one made with a certificate. That has its own guide: How to sign a PDF with a digital certificate on a Mac.

Should you save over the original?

Usually not. When you sign, Better PDF asks where to save the signed copy, and suggests <name> signed.pdf. Keep the blank form; you will need it again next year.

For a form you filled but did not sign, ⌘S saves in place and ⇧⌘S saves as a new file. Answers in real fields are stored as field values, so anyone opening the file in another PDF app sees them and can still change them.

What does “flatten” mean, and when should you do it?

Flattening turns form fields into ordinary page content. The answer stops being a value in an editable box and becomes text printed on the page, like the rest of the form.

You flatten when:

• the recipient should not be able to change your answers,
• the form looks different in different apps (some viewers draw field values in their own fonts, or not at all),
• a printer or an upload portal mangles field values.

In Better PDF, choose File › Flatten Form Fields…. A card explains that the answers will no longer be editable, and you can undo until you close the document. Flatten before you sign with a certificate. Flattening rewrites the pages, and a certificate signature is a record that the pages have not changed since signing.

When do you need more than a form filler?

If your office runs forms with heavy scripting, collects signatures from a dozen people through a sending service, or needs form fields designed from scratch, a full form builder or a signing service is the right tool for that job. For filling a form someone sent you and signing it, you do not need a subscription.

The shortcuts in this post, and the rest, are in Help: Sign with a certificate or USB token and Open and read a PDF. Better PDF needs macOS 26 or later; download it here.

Questions people ask

Can I fill a PDF form on a Mac for free?

Yes. The built-in viewer fills forms that have real fields, and Better PDF fills both those and flat, scanned forms at no cost, including signing.

Why can't I click into the boxes on my PDF form?

The form is flat: the boxes are printed lines, not fields. Use an app that lets you type anywhere on the page, such as Fill & Sign in Better PDF.

What does flattening a PDF form do?

It turns the field values into ordinary page content, so they print and display the same everywhere and can no longer be edited as fields. Keep an unflattened copy if you may need to change an answer.

Should I flatten before or after signing?

Before. Flattening rewrites the pages, and doing it after a certificate signature would break that signature.