Hi,
If you are using workspace to initiate a process with some attachments. Then you have to do the following in the User Action:
(a) select the "show attachment window to this task"
(b) select "copy notes and attachments from previous task"
In case of some other custom applications you have to post the full PDF document to the process then extract the data from the PDF document and using assembler service to extract the attachments from the PDF document.
Regards,
Waqas