You have a PDF form and don’t want to print it and write by hand, or you need to add a name, a date or a logo to a PDF. Here is the difference between fillable and scanned forms, how to type Thai onto a PDF, and a warning about “deleting” text.
In short
- The form has fields: use fill PDF form to type Thai into fields, tick boxes and pick options.
- A scanned form or any other PDF: use edit PDF to place text anywhere, add a picture or logo, highlight, draw boxes and write with a pen.
- Hiding confidential data: don’t cover it with white; use redact PDF.
Every tool runs in your browser. Your file is not uploaded.
Fillable forms vs flat forms
- Fillable (interactive) forms: the PDF 1.7 specification calls them AcroForms, a collection of fields for gathering information from the user. Adobe says they have highlighted fields such as text fields, checkboxes or radio buttons.
- Flat forms: Adobe describes these as scanned paper forms or PDFs with no interactive fields, where you add text boxes yourself.
Thai examples: we opened the 2569 ภ.ง.ด.94 form from the Revenue Department’s forms page and found it is a fillable form; several Social Security Office forms we checked were flat, with no fields. The Revenue Department’s own FAQ says that if you can’t type and the pointer is a hand, that form is still being prepared, but you can download it to use instead of the paper form.
Filling in a fillable form
- Open fill PDF form and choose the file.
- Type Thai into the fields, tick boxes and pick options.
- Save it as a filled-in PDF.
The result is locked as a completed document so Thai text shows correctly everywhere and it’s ready to print or send. Apple suggests something similar in Preview on Mac: save via File › Print › Save as PDF so additions can’t be edited. Keep the blank form in case you need to fill it in again.
Typing onto a scanned form or any PDF
- Open edit PDF and choose the file.
- Pick the text tool, tap where you want the text, type Thai in the side panel, then use the select tool to drag it onto the line (one box per line).
- Add a picture or logo, highlight, draw a box or write with the pen as needed.
- Download the new file.
To sign it as well, use sign PDF, and read about electronic signatures in Thailand.
Why you can’t edit the existing text directly
Microsoft explains that PDF is a fixed format: it stores where text, pictures and graphics sit on a page, but not necessarily how they relate. Even in Adobe Acrobat, editing text in its original font requires that font on your computer, and Preview on Mac can’t edit a PDF’s text at all, only mark it up.
What works
- A few words: white out the old words and type the new ones on top.
- Lots of changes: convert with PDF to Word, edit in Word and save a new PDF. Microsoft warns the converted file may not look exactly like the original, and pages that are mostly charts or pictures may come through as images whose text can’t be edited.
White-out doesn’t really delete anything
A white or coloured box on top only stops the text being seen; the original text is still underneath and can be copied out.
- The NSA says covering text with black boxes works for paper but in general is not effective for computer documents, and is the most common mistake.
- The U.S. Court of Federal Claims explains that a black box laid over data merely hides it: anyone can copy the box into a word processor and see the text underneath.
For confidential data such as ID card or account numbers, use redact PDF, which removes the text under the black bars from the file.
Note
This article is based on Adobe, Apple and Microsoft help pages, Adobe’s edition of the PDF 32000-1:2008 specification (copy in the Internet Archive), documents from the NSA (copy in the Internet Archive) and the U.S. Court of Federal Claims, and the Revenue Department website, read on 30 September 2026. Whether each form has fields comes from our own check of the files that day.
