Which PDFs can be filled in? (fillable fields or flat PDF)

Only PDFs with fillable fields (AcroForm) are supported. Flat or scanned PDFs are not.

What it is for

Know in advance whether your PDF form will work with “Fill in a PDF”.

None.

Open your PDF in a PDF reader.
Try clicking in a form box: if the cursor types text there, or if you can tick a box, the PDF has fillable fields (AcroForm): it is suitable.
If nothing is clickable (fixed text, scanned image, photo), it is a “flat” PDF: Formtool cannot fill it in.
If the file is password-protected, remove the protection in your PDF reader before adding it.
An old dynamic form (XFA) without AcroForm fields is also rejected: ask the organization for the “fillable” or “printable and fillable” version.

You know whether the PDF can be added to “Fill in a PDF” and avoid the rejection “This PDF has no fillable fields (flat PDF).”

The vast majority of recent official forms have fillable fields: look on the organization’s website for the “fillable” version.
Signature fields and buttons are not offered: signatures, stamps and boxes reserved for the administration still have to be completed in a PDF reader.
Filling in flat PDFs (without fields) is not offered for now.

“This PDF has no fillable fields (flat PDF). Use the version of the form with fields.”: The PDF is flat, scanned, or its fields are locked. Use the version with fillable fields.
“This PDF is protected (encrypted): remove the protection before using it.”: Remove the password or encryption in your PDF reader, save, then add the file again.
“This file is not a PDF.”: Choose a real .pdf file.
“Unreadable PDF (…)” or “Unsupported PDF format (…)”: Reopen the PDF in a reader and save it under a new name, or get another version of the form.

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