Why are Adobe Acrobat files (.pdf) considered good for longterm archiving, in terms of future compatibility? Aren't they just another proprietary file format?

BTW the freeware converter PrimoPDF has worked well for me to make PDFs from any other type of file. I'm sure there are other programs out there as well.

Yes, Adobe Portable Document Format (PDF) was invented by Adobe, but I’d hardly call it “proprietary”. The previous link is Adobe’s description of the format and describes how they are attempting to standardize the format even more.

Basically, PDF is a good format for storing documents because you do not have to depend on the host system (the computer you’re plugging your USB drive into) that much to be able to open and print the document. There are portable applications, such as Sumatra PDF Portable that will allow you to open and print a PDF document without even having Adobe Reader installed on the host PC system. PDF is also advantageous because you can secure your documents any way you need to. (Security features vary with the PDF creation method). However, the main advantage of PDF is a lovely thing called backwards compatibility. PDF viewers years from now will almost certainly still open the older-format PDFs.

The only real disadvantage to PDF documents are that they cannot be modified on the fly. (Maybe Adobe Acrobat can do this. I don’t know. I just installed Acrobat yesterday.) Any documents that get modified frequently may be better to store in their native .doc or whatever format instead.

I've noticed that pdf's are not the perfect portable format, sometimes not looking the same on one system as they do another and other times not being as backwards compatible as they should be.
Plus you can't easily edit them.
I carry my important files in openoffice format and carry portable openoffice along with them. It has the ability to save to pdf so I can make that final read only copy on pdf format once I've finished editing.

PDF's are great if you need to preserve the original formatting, etc. or if you have vector graphics such as a mechanical drawing.

However, if its just info like account numbers, phone numbers, etc. then I think that a plain old text file would be be most portable.

Instead of putting that info on a flash drive, why not just create a gmail account and e-mail the documents to it?

If you want other people to have access to some of it, you could just get a little dog tag engraved with the name of the g-mail account and the password and put that on your key ring. Something like "Medical information at xyz@gmail, password 1234"

You could, of course, encrypt your banking records or whatnot if you don't want people to have access to those.

I have a gmail account set up and tied to my PLB and I send updates to that account re my travel plans, etc. so if my PLB is activated rescuers can access that info in my g-mail account.

The only downside I can see is that it would not work where people do not have internet access or if the internet is no longer functioning. But I think chances are pretty good that anyone with a computer with a USB drive can figure out a way to get onto the internet. Heck, even if not, they could just call someone and have them access the internet and read them the medical info.

You don't want to rely on any more third parties than necessary. Sure you could use gmail as another backup but since its not under your control don't make it your primary method.
Look at what has happened to other free services, yahoo for example turned to crap, msnhotmail lost my mail twice with simply a message saying sorry your mail was lost.

Eugene - I agree in principal, but I have at least as much faith in Google's ability to maintain my data as I do in a flash drive on my keychain.

Just sayin'.

Basically what I'm saying is use both, don't rely on one or the other.