Maybe it is just the recruiter. I saw a printed copy of my CV with their header on in one interview, so I assume they want to edit it to do that.

That's exactly why they want it as a Word document. That's what they use to produce their in-house resumes for distribution, and they don't want to waste ten seconds on opening an HTML or PDF resume in Word and selecting "Save As... Word document". They want to create their own resume, with your name on it, that is loosely based on your actual resume, so they can send it out to hiring managers.

It's very safe to say that if you don't know how to open and edit a PDF document, you have no business being a tech recruiter. Anyone foolish enough to be represented by such a person while looking for software jobs is going to have a bad time.

If you're seeing a demand for it in Word format, they're a recruiter and a lazy one at that.

Most in-house guys accept PDF. I explicitly tell recruiters that my resume is typset, so they have a choice: a PDF or a LaTeX file that nobody will ever make heads or tails out of. I do not even know if LaTeX has a .doc plugin.

If you're seeing a demand for it in Word format, they're a recruiter and a lazy one at that.

Most in-house guys accept PDF. I explicitly tell recruiters that my resume is typset, so they have a choice: a PDF or a LaTeX file that nobody will ever make heads or tails out of.

Don't do it! Shady recruiters ask this so they can edit your resume without telling you. Only send PDFs to recruiters, the shady ones won't bother with those.

If what I have heard is correct, it is because some resumes scanning softwares have trouble with PDFs. They often default to asking for Word because they know it works.

I assume it's so they can modify it and re-send it out to other companies.