I'm entering this as a question even though I found the solution in the hopes that it helps the next person.
Using Excel on a Windows PC, I tried printing a document to PDF that I'd previously had no issues with, but all of a sudden when I tried printing to PDF there were seemingly random borders that were missing in the print preview. I tried printing to PDF anyway since sometimes the print preview hides some borders then the PDF comes out fine anyway. This wasn't the case this time - the PDF also had the borders missing. What was especially strange was that when I printed to an actual printer, the borders showed up in the print preview and the copy that was printed out, but I needed to send the file via PDF and printing a hard copy then scanning it back in wouldn't have worked well. What could be done to get the borders to show up in the final printed PDF and what was causing them to disappear?
I came here and found this article, and I tried several solutions to no avail.