I may not be clear on what you are asking here but I'll try an answer anyway since that's the type of guy I am.
If you have PDF files on your old computer, you will need to transfer them to your new computer. You can use a flash drive or CD if needed.
But again, I think I'm not getting what you are really wanting to know. If I'm not, can you give us some more details?
If you saved them in the cloud (Acrobat.com), then you don't have to worry about your files.