Any advice on creating PDFs?

I've been trying to PDFs of my text documents that have both a light background and a dark background, but both Word and my Google-fu have unfortunately failed me when it comes to finding an efficient way of getting both. Word simply gives me PDFs with a light background no matter what I do, as do most of the other programs I've found. 

I have considered just inverting the colors of those PDFs to get one with a dark background, but doing that for a large number of documents quickly gets tiring. The easiest methods of doing it also increase the file sizes by a lot (there has got to be a more efficient way of doing it than what I found), so it's not really worth it.

I know there are authors here on Royalroad that use PDFs both with dark and light backgrounds, so I assume they have decent enough solutions for this. I mean, there has to be a better solution. I just haven't found any yet.

So, anyone got any advice on what I could do? Or better yet, sitting on the exact magical tool I need in this situation, perchance?

Screw word and its inexorable language settings that literally never work as they should if you use more than one editing language.