If a link is to a pdf and so opens in a pdf reader embeded in a proton page, I can click the Download button and the file will download with the proper file title. However within the reader is a download arrow. If you were to click on that to download the file the file name is a garbled number and letter sequence. I've tried this with another cloud drive service which the process looks nearly identical except that clicking the download arrow retains the file name. I'm guess most people would hit the Download button but as a frequent user of pdr readers I habitually hit the download arrow, which garbles the file title in the Proton Drive's case.