How to make a PDF Form uneditable?

Question

Is there a way I can fill out a PDF form in Ubuntu and safe it in a way that one cannot alter it longer? I remember there is such function on some other OS (e.g. macOS), but it seems like the Ubuntu document viewer is not able to do that.

Answer 1

I am assuming that you want to get rid of the "fillable fields" in that form.

A way to do this is to convert the pdf into a jpg, and converting it back to a pdf.

To convert, enter the command

convert -density 300 /path/to/your/form.pdf picture.jpg

The -density 300 ensures that the quality of the resulting JPG remains good.

Then convert it back to PDF with

convert /path/to/picture.jpg filename.pdf

The resulting PDF would not anymore have any fields to be filled.

Of course, someone may edit it in an image editor to change the contents.

If someone can view the form, you cannot prevent them from editing it (even if it is password protected so that everyone can view, but only the people with password can edit, then one can take a screenshot and edit it with photo editing software like GIMP to change the contents).

If you have problems converting it due to "security policies", follow the guideline here: https://stackoverflow.com/questions/52998331/imagemagick-security-policy-pdf-blocking-conversion