How to attach more than 10 files to a Notes document
By default, the maximum number of files that can initially be attached is 10.
What you need to do is to add as many rows as you want to a table on a "SwAttachments" subform. Now, you should copy the last row in the table to each of these newly created rows and change field names to Sw...._11 (and _12, _13 respectively). In additon, you should change "hide-when" formulas for every added row and formulas/code on the fields in those rows.
Of course, you will have to change form's PostOpen and QueryOpen events to allow more attachments on it (Source.Document.SwMaxAttachments = xx).
Note that the maximum number of attachments is actually 99.