Can attachments be attached to a ITAM object using the ITAM WebServices?
Where to find information on how to upload files to ITAM and link/add them as attachments to Legal Documents via the ITAM WebServices?
There is no WebService method to add ITAM attachments.
This is a limitation on current releases.
Please log a 'Idea' on Communities to request an enhancement for such a method to allow the attachment to an already existing object. See 'Additional Information' for links\video on how to create an Idea.