Since the translation (i.e. the text) is out of copyright, you can basically do whatever you want (the OCR'd text is supposed to be word-for-word identical to the uncopyrighted original text, so you don't have to comply with the license on the scan - for that matter, the scan may not even be subject to copyright protection in the first place). However, you should consider some common use cases, and ask yourself what rights you want the reuser to have:
- Suppose someone wants to change some of the formatting of your LaTeX, for example to meet the stylistic requirements of some publication. Do you want to force them to license the resulting document as GPL?
- Suppose someone wants to reword the document, to bring it in line with a more modern variety of English (e.g. several decades in the future). Should they be forced to use GPL?
- Anyone who doesn't want to put up with your licensing restrictions can always just strip the LaTeX commands (so they just have plain text) and redo the formatting from scratch. Since the underlying text is out of copyright, they don't need to comply with the GPL. Does using the GPL really accomplish anything, other than inconveniencing people?
It's my opinion that using a copyleft license is more trouble than it's worth in a case like this, but you may come to a different conclusion. If you really want to use the GPL, you could write an exception, for example:
As an exception, you may process this document through any LaTeX compiler, and distribute the resulting PDF or PostScript file(s) under [license]. If you modify this document, you may extend this exception to your version of the document, but you are not required to do so. If you do not wish to do so, delete this exception statement from your version.
(Be sure to identify a specific Creative Commons license. Do not just say "Creative Commons 4.0" - otherwise someone might choose e.g. CC-BY-NC-ND, which is probably much more restrictive than you wanted.)
However, I'm not thrilled with that option, for multiple reasons:
- It's a form of crayon license, and those are generally problematic.
- It's specific to LaTeX and the PDF and PostScript formats. You might be able to remove those format specifications from the text, but that might make it so ambiguous or general that it becomes hard to tell what is permitted and what is not. Copyright lasts for a long time, often much longer than individual technologies. These three technologies have been around for a while, so they might be less susceptible to obsolescence than other formats, but I still don't like tying the license to them, just in case.
- The text is not under copyright, so you're not really protecting much in the first place. I just think this is too much legal complexity for too little benefit.
Instead of the GPL, I would suggest a simple permissive license such as CC-BY, or one of the other Creative Commons licenses. If you really want to be maximally permissive, you could also choose CC-0.