How to Insert Attachments to My PDF File?

Hi everyone, I’m looking for a reliable way to insert attachments into a PDF document. I have a few supporting files (like images and documents) that I want to embed directly within my PDF so everything stays in one place. I tried a tool called FreeViewer PDF Attachment Inserter, and it worked quite smoothly for adding attachments without affecting the original formatting.
However, I’m curious if there are any other effective or free methods available—maybe using built-in options or other tools? I’d appreciate any suggestions or recommendations based on your experience.