This is probably a trivial question, so I apologise for that, as well as for my lack of printing media terminology, but the case is that I don't manage to figure out which is the right way to print crop marks for a specific page size while still printing in standard A4 paper.

I'll try to explain it better: I'm writing my PhD Thesis with Prince. I wanted it to have the appearance of a book, and I was considering using a page size of 7 x 8.75 inches. But I want to print on my own before sending it to the publisher for binding. They have said to me that I can do it, printing in standard A4 paper, as long as I print it with crop marks.

So the question is: how can I do this? Must I specify A4 as the page size and then make calculations to know where to put the crop marks (I suppose that using the properties prince-bleed and prince-trim)? Or is there an easier way to do it, specifying the actual final page size (let's say, 7 x 8.75 inches) and letting Prince calculate where to put the crop marks for printing in A4?

Any advice would be very, very helpful, since I've spent a few hours but I'm still not sure which is the procedure in these cases.

Thank you very much in advance.

The physical sheet of paper (media box size) is the size of the CSS "page", eg. size: A4, plus the prince-trim and prince-bleed sizes.