Okay, what’s this post about ?

You know, when you need to, like, apply for a flat. Or a bank loan. Or many other things.

At some point, you need to provide various documents, to prove various stuff.

“Sure”, you think, “that’s annoying, but what’s your point ?”

Identity theft

Yeah.

Hasn’t happened to me, but nowadays, not-so-nice people sometimes put online fake flat offers, often too good to be true, just for you to apply, and send just about every information about yourself.

And then, they make a loan in your name. Or something similarly bad.

Anyway. Here are two ways to reduce the risk of this happening to you :

• Be cautious who you send your documents to. If it looks too good to be true, well … it probably is
• Add some kind of stamp on the documents, to prevent their re-use in a different context

I can’t help you much with the first one.

I had a very hard time with the second, even though it sounds like it should be easy.

So, here are my notes.

Some basic pdf handling with linux CLI

Here’s what I’m trying to do :

• concatenate all my pdfs in a single one

  • not exactly necessary, but it tends to be appreciated, and easier to handle

• add a semi-transparent stamp, saying like “flat search 2023”

  • While the date might be considered reduntant (the documents will be obsolete soon enough anyway), the purpose of the document is essential.

We’ll be using libreoffice, and pdftk, both of which should be present in most distribution’s package managers.

Okay, here are the instructions :

• install libreoffice and pdftk

• create a new LibreOffice Draw document

• add the text you want in it. like, “flat search 2023” in my example

• Rotate the text and increase its size so that it fills most of the page (click twice on the text box border to be able to rotate it)

• Select your text, and make it a color (I chose green), with like 50% transparency (Format/Styles/Edit Style/Font Effects)

• Select your text box (and ensure it is selected before next step)

• File/Export/Export as PDF

  • Export only selection (otherwise you’ll get a white background, not a transparent one)
  • export it as stamp.pdf

• Get all the documents that you want to concatenate in a single “input” directory, in pdf format

  • By the way, you can split a given pdf in separate pages with pdftk input.pdf burst, if you need to.

• Name them so that the alphabetical order is the order you want them to be concatenated in

• `pdftk path/to/input/* cat output - | pdftk - stamp path/to/stamp.pdf output output.pdf

• Open output.pdf and look if it looks like what you want

If it doesn’t work immediately, tough luck.

A few elements that could help you debug :

• Split the command in two, and use an intermediate file instead of piping the concatenated-but-not-stamped file
• Add verbose at the end of the commands