How to print a rich text on predefined sheets?

Question

Hi all,

I'm currently stuck with the following problem:

The user has to write in a rich text box and the result must be printed on some predefined sheets. These sheets, have 50 lines (25 lines in each page)and they also have a specific line spacing between them.
Finally, the user must also be able to choose in which line he wants to start the printing, for example, he decides to start printing in line 20 and he has 10 lines to print then: the first 5 lines should be printed in the first page and the remaining 5 in the page.

The question is, how can I handle the number of lines in the page, the line spacing and also give the user the possibility to choose where to start the printing? I went through a lot of pages explaining how to print files but I couldn't find one describing how to control line spacing and more important the starting line of printing.

Thanks in advance,
Nahuel