It is possible, instead putting catalog attachments in SDM as a link, saving the file attachment in SDM attachments folder?
I've dug into this a bit, and came across an older communities post related to adding Catalog attachments to Service Desk Manager, at the following link:
How to view service catalog attachments in service desk
The solution contained in the above link requires an instance of PAM, in which you can create a workflow that will download the SC attachment and upload it to SDM. Please take a look, and feel free to reach out with any questions you come across!
Do you require any further assistance on this topic? If not, please mark Eddie's answer as correct so that this thread can be closed.