Many funders require a conference-issued certificate of attendance & presentation, perhaps with specific requirements such as "conference headed paper" and "organiser signatures". The closest Indico comes to this is the Badge system, but this does not have access to the participant's presentation(s) title, type, or date. This information is available for each contribution individually in the Contributions list, but this does not meet some funders' requirements of heading, signature, etc.

It would be ideal if there was a built-in Certificates facility that could be enabled, to provide each attendee with a certificate PDF customisable by the meeting organisers to add signature images etc. if necessary. Much of the backend could presumably be shared with the badge facility, just extended to include the contribution details currently available via the Contribution pages. I expect that a certificate per contribution would also be acceptable, provided the heading / signature customisations are possible.

As certificates are essentially a personal document for the contributor, I would not think this should be publicly available -- either generate+email-able via the registration / contributor lists, or accessible specific to the user's Indico login.