PDF text originating in Photoshop becomes “soft” when it gets rasterized. This happens if you change the blending mode from normal to something else or apply an effect, or use faux bold or faux ital, text warp, etc. So, make sure you don’t do anything like that which has to be rasterized in PDF rather than the PDF using the font as-is.
You can make a crisp PDF circle in Photoshop by making it a shape layer rather than a filled selection.
There may be some additional PDF setting you have to select to retain vector information for shape layers, I don’t recall off the top of my head.