In my app I have a Terms and Conditions page which I would like every user to sign and download a copy of it (no specific file format for download, anything is acceptable). The sign can be done digitally. Is there any way I can add this feature? I cannot find such feature in Glide, so what 3rd party platform would help me do it?
Use the Glide signature component.
I would recommend the same thing as @Jaime on your onboarding flow, but if you need to store the documents WITH the signatures then SignRequest is a good alternative.