How to Fill Out a PDF Form Online, Fillable or Not

What is the difference between a fillable and a flat PDF form?

A fillable PDF form contains real interactive fields, technically called AcroForm fields. The creator of the form defined text boxes, checkboxes, radio buttons and dropdowns at specific positions, often with names like 'first_name' or 'date_of_birth'. When you open such a form in a capable viewer, you can click into a field and type, and your answers are stored as field values inside the PDF.

A flat form only looks like a form. The lines, boxes and labels are printed on the page like any other content, but there are no fields behind them. This is very common with scanned paper forms and with forms exported from a word processor without adding fields. Clicking on a line does nothing because, as far as the PDF is concerned, it is just a line.

The quickest way to tell them apart: open the form in Fill PDF Form. If it finds fields, you will see them ready to fill. If it finds none, you are dealing with a flat form and should use a different approach, which we cover below.

How do you fill out a fillable PDF form online?

For forms with real fields, our Fill PDF Form tool is the most direct route. It reads the fields in your PDF and lets you type into text fields, tick checkboxes, choose radio options and pick from dropdowns. Everything runs in your browser, so a form full of personal details, such as your address, ID numbers or income, is never uploaded to our servers. There is no account and no watermark.

We recommend reading the whole form once before you start typing. Many official forms have conditional sections ('complete part C only if...') and it is easier to skip them deliberately than to realise halfway through that you filled the wrong page.

• Open Fill PDF Form and drop in your PDF.
• Click into each field and enter your answers; use Tab to move between fields where supported.
• Tick checkboxes and choose options for radio buttons and dropdowns.
• Decide whether to flatten the form (see below), then download the filled PDF.
• Open the result in another viewer to confirm every answer is visible.

What should you do if the PDF form isn't fillable?

If the form has no fields, you can still complete it on screen by placing text on top of the page. That is exactly what our Edit PDF tool does: you add text boxes wherever you like, adjust the size, and position them on the lines or inside the boxes printed on the form. You can also draw checkmarks or crosses in tick boxes.

This takes a little more care than a fillable form, because you are aligning text yourself. Our tips: zoom in while positioning, use one consistent font size throughout (10 to 12 points usually fits standard form lines), and write in capitals if the form asks for block letters. For scanned forms that are slightly skewed, place each answer individually rather than trying to align a whole column at once.

If a flat form is something you fill in regularly, it may be worth asking the organisation that issued it whether a fillable version exists. Many do publish one, and it saves everyone time.

Should you flatten a filled PDF form?

Flattening converts form fields into ordinary page content. Your answers stay exactly where they are, but they are no longer editable fields: they become part of the page, just like the printed labels.

We generally recommend flattening when you are sending a completed form to someone else, and not flattening when you are saving a draft you plan to update. Some organisations specifically ask for an unflattened form because they extract field data automatically; if the instructions say so, follow them.

• Flatten when submitting: the recipient sees exactly what you entered and cannot accidentally or deliberately change your answers.
• Flatten for compatibility: some viewers, especially on phones and in email previews, display field values inconsistently. Flattened answers look the same everywhere.
• Do not flatten drafts: keep an editable copy so you can fix a mistake later without starting over.
• Keep both versions: we save an editable copy for our records and send the flattened one.

How do you sign a PDF form after filling it?

Most forms end with a signature line. Once your answers are complete, open the filled PDF in our Sign PDF tool, draw, type or upload your signature, and place it on the signature line. Add the date next to it if the form asks for one. Like our other tools, signing happens locally in your browser.

The order matters. We fill first, flatten if needed, and sign last, so the signature is applied to the final content. If you sign and then change an answer, you are effectively changing a signed document, which is exactly what the recipient wants to be sure did not happen.

A note on legal weight: a drawn or typed signature image is an electronic signature in the everyday sense and is accepted for a great many forms. It is not the same as a certificate-based digital signature, which some government and financial processes require. If the form's instructions mention a specific signing service or certificate, use that.

What are common problems when filling PDF forms?

Most issues we see come down to a handful of causes, and each has a simple fix.

• Answers disappear in another app: the viewer is not rendering field values. Flatten the form before sending.
• Text is too long for the field: shorten it or use abbreviations; fields with fixed size may cut off text rather than wrapping.
• Form is password protected against editing: you need the owner's permission or password; Unlock PDF only helps with files you are entitled to open.
• Fields appear but will not accept input: some forms use advanced scripted fields; try filling it as a flat form with Edit PDF.
• The upload portal rejects the file: check the size limit and compress it, and make sure it is a standard PDF rather than a scan saved as an image.

Frequently asked questions