I suspect the basic process of generating recognizable and readable files will be quite simple (you can do it in plain text Notepad), but calculating the formatting will be a much greater challenge. I don't know that that can be done automatically in PDF.
As a general example of document formatting: the MiKTeK package is an 80MB download for Windows. I don't know what a minimal package of pdflatex would entail (it's free software, so you should, in principle, be able to port it to your platform!). It will certainly fit on a flash drive, but that doesn't necessarily mean you would want to use it. It will be file-intensive, and run very slowly, reading and writing from such limited media. The processing power is also a bit on the thin side, but to your advantage, LaTeX comes from the days of sparse RAM, so an ARM M-something should be more than adequate. And being file-intensive, you may prefer a platform that can support Linux embedded, which will consume more program storage, RAM and CPU cycles.
Perhaps a worst case would be, you have to add Flash and RAM to your project (using a processor which supports an external memory bus). But I'm guessing that's better avoided.
What is the end purpose? You may find it vastly superior to use a different standard. There isn't a commercial computer device in existence which doesn't support HTML -- look it up on your phone, look it up on your desktop, look it up on your printer (ehh, possibly).
HTML and LaTeX share some common background, and have a certain amount of equivalency as markup languages (PDF can also be structured as markup I think, but you still have to calculate everything, whereas HTML and LaTeX have defaults, and simple commands allow changes to global and local formatting). The biggest difference being, HTML is always rendered on-demand in the browser, while LaTeX needs to be compiled, so the burden on your system is exponentially smaller. It should be no surprise that embedded systems such as routers easily offer HTML over HTTP as standard portals.
Tim