I repeatedly try to download pdf of 2018 return and save to my computer. It saves, but always as an unreadable notepad file. Can I get the pdf file so I can print?

Your Edge browser changed the file extension from .pdf to .txt.  Rename the file extension to .pdf so a PDF application can open the file

Some browsers occasionally download it with a .txt (text) extension by mistake.  Try changing the file extension to .PDF and see if that works.  If not, try downloading the PDF with a different browser.