Formula ReadFile will allow you to get files from your local file system. It takes two parameters, a directory and file name. It will go to the local filesystem on the computer where the formula is evaluated and read the file content into an internal binary object for the transfer.
Example 1:
##ReadFile('\share01\files', 'image001.jpg') ---> read file \share01\files\image001.jpg
Example 2:
##ReadFile('C:\invoices', 'INVOICE_'+"No"+'.PDF') ---> read file C:\invoices\INVOICE_A001001.PDF (if the "No" field has the value "A001001" for example).