The easiest way to simulate how a PDF A4 letter would look like on a desk?

I'm preparing a start-up and have to send some corporate letters to potential business partners. I have already designed it and filled with contents, and exported to PDF.

Now I'd like to see how it'd look like on paper - the thing is that I have no colour printer at the moment. So I've seen all those mock-ups, where somebody's mobile app design is nicely pasted onto a photo of a guy holding a phone or an iPhone lying on a desk along with leaflets, some letters and other marketing materials of your company to make sure the design is congruent.

Is there any, preferrably online, tool that I could send my PDF to and get a picture of it on a desk or anything in return? I know that usually Photoshop/AI are used for that, however I'm not going to spend money on this at all. Or maybe some tricky how-could-I-not-think-about-it way to do this thing?

Thanks!