For some reason when I created a document in MS Word using Times New Roman, then converted it to a .pdf, the font in Perusall changed to something quite different and hard to read, i.e., the kerning was all screwed up and squished. In Adobe it looked fine, but not in Perusall. This happened with multiple documents. I changed the font in MS Word to Baskerville, and now the .pdf in Perusall looks fine.