Answer:

There is currently a limitation of approximately 250 characters for the path and folder name when linking to a PDF file in EndNote X and later. With the relative linking option active, your PDF files will be copied to a PDF subfolder of your EndNote library’s .Data folder. Here is an example PDF file and path that would be created:

C:\Program Files\EndNote X\Examples\paleo.Data\Pdf\ARTICLENAME--Author and Author-ArticleTitle4252373761\ ARTICLENAME--Author and Author-ArticleTitle.pdf

This path includes the location of the EndNote library as well as the folder associated with the PDF file that EndNote creates and the name of the PDF file. The path and name of this PDF file combine for over 100 characters. If the EndNote library is stored in a more nested location with multiple subfolders, folder and PDF file names are longer, and this error happens.

To resolve this issue, you can move your EndNote library and associated .Data folder to another location on your hard drive so it is not nested deeply, like the following:

C:\Libraries\paleo.enl
C:\Libraries\paleo.Data

Alternatively, you can shorten the name of the folder and/or the name of the EndNote library. All together, you should try to keep the total number of characters under 250 to allow the link to PDF option to work.