Hi Juan,
Adding further onto the above points, if you are considering a scenario, wherein an attachment field is already present on the Idea screen, with a document stored in it and you would need to refer to that document, you could look into the following approach:
a) Query the CLB_DMS_FOLDERS (will contain the folder name, storing the document), CLB_DMS_FILES (will contain the file information), associate it with the object wherein your custom attachment field is present. For example, if the attachment attribute (example: attachment1), was created on Investments and being referred to on the Idea screen, then you will need to associate odf_ca_inv.attachment1, with the above tables, to locate the folder and respective files
b) Create a GEL script in order to read the file data and process it further
There's a reference to similar discussion on the following link, in case if the scenario matches ->
https://cdn2.hubspot.net/hubfs/2652075/2017%20Rego%20U%20Presentations/Technical/PRSS1010-Read%20an%20Attachment%20Flat%…
Reference to handle an attachment in a GEL script:
Attach document from GEL script?
Regards,
Samik