Found a simple solution: Set output style to “RefMan (RIS)”. Export all refs in your original library using this style to a file (it will be in text format). Open this in a text editor (Word may also work) and search for and replace the old absolute path with the new absolute path (on the new computer). Save as a different file. Import this file into a blank new Endnote library. The paths to the pdfs should now work.