How can I obscure the text in a PDF file (e.g. “greek” it, or replace the text with Lorem Ipsum)

Question

I have some lengthy PDF files produced for one client that I want to use as samples to send to another client. However, the text in the PDF is commercially sensitive, so I don't want to send it as-is.

I'd like to obscure the text so that the document still has the same overall look as the original, but with either nonsense text (lorem ipsum ...) or with the text "greeked" so as to be difficult to read. All the other parts of the document should remain untouched, i.e. I don't want to spoil the artwork, etc.

I know that Acrobat can redact the text - but that simply blacks it out completely so that it no longer looks like text. That's not what I'm after. I want the document to look like a real document - but not contain the sensitive material.

Is there a tool that does this?

Answer 1

If you purchase Adobe Acrobat Professional it can do this. Either by changing the pixels in scanned PDFs (I think, it may just draw a white box over the top) or by altering characters in a generated PDF.

For a free solution (only done this under Linux, YMMV) you could convert the PDF back into PostScript and (if you're lucky) you will see bits of the text you can edit and recreate the PDF, and for scanned PDFs you could convert them into image files, edit the images with GIMP and then convert them back to PDF.

Either method (Acrobat or PostScript) that changes the text doesn't usually mess up the typesetting (by the time the PDF is produced each element seems to be fixed at an absolute position on the page) but by the same token the changed text usually looks horrible as the previous characters' typesetting is still in effect (resulting in uneven line widths, etc.) And you usually have to change it in small lots (sometimes a single character at a time) so it's not suitable for a document of more than a page or two unless you have the patience of a saint.