I would like to add to the comments of Ray Davis on the subject of PDF’s incongruities with the Web. My argument is that the "Portable" in PDF doesn’t always deliver. That is, if the document was not saved with all its fonts, there is a chance that it won’t print out correctly at all. I have had this problem downloading documents to my Mac, especially with documents containing equations or tables. I can print from a PC fine, but it seems that the Mac has a different default font set that foils my printing efforts.
Ray’s message seems to come through clearly here, too. HTML is designed to deal with font difficulties by using tags that are resolved locally into available fonts. I don’t know if HTML deals well with equations in all cases, but it seems to have done so on the many HTML documents with equations that I’ve seen up to now.
I would recommend that instead of singing the praises of PDF, you let us know how to deal with PDF intelligently. It is a special challenge, I am sure, because the person who reads PDF can’t change the fonts that were saved with the original document. And in my case, these aren’t graphic folks who think about fonts all the time, but researchers who just want to make their ideas more widely available and have little idea the impact that fonts have on transmitting those ideas.