I am a big fan of the report builder in Google Ad Manager (formerly known as Doubleclick For Publishers or DFP). Not only can you create powerful, bespoke reports - you can also share them with other users in your Google Ad Manager account. Here's how owning and sharing reports works, and what the main limitations are.
The first thing to note is that a report in Google Ad Manager is effectively just a configuration - a group of settings (date range, dimensions, metrics and so on). A report can be run to produce what Google calls 'report results'. You might run the same report at different times and get different results. It is also possible to share results, but I'm not going into that today.
Anyway, create a report by going to Reporting > Reports and then clicking New report. Every report needs at least one dimension and one metric before it can be saved. For example, a simple report might have the dimension 'line item' and the metric 'total impressions'. This will tell you how many impressions have been served for each line item in the given date range (which is 'yesterday' by default).
Once the report is saved, you become its 'owner' and you will be listed as such in the Reports page:
When creating or editing a report, you are able to add 'Editors' - also referred to as 'collaborators'. To add someone as a report editor, they must already exist as a user in your Google Ad Manager account (to check, go to Admin > Access & authorization). Just start typing their name or email address in the 'Editors' field, then pick them from the auto-suggest that pops up:
Your report will then be visible to that user when they log in and go to Reports. You will be listed as the owner.
(Bizarrely, as you can see in the screengrab above, the auto-suggest happily suggest that you add yourself as editor to a report for which you are already the owner. This doesn't achieve anything, and in fact if you do make this change, you won't be listed as an editor the next time you go into the report.)
It's important to understand that the report is shared in the most literal sense. If the other user changes the report's settings, they will change for you too. If they delete the report, it will disappear permanently from your Google Ad Manager account too.
At this point you may wonder whether a user's ability to edit a report is tied to their user role rather than anything relating to a report itself. As such you may think that you are safe sharing your important report with a user that has the pre-set role of 'Executive', which Google defines like this:
Executives can view everything throughout GAM and can run reports, but cannot make changes
Executives may not be able to make changes to line items and orders, but they very much can make changes to (and delete) reports - including reports belonging to other people. In fact, any role which includes the ability to "create and view reports" also has the ability to modify and delete reports that have been shared with them by other users.
The other main limitation with report sharing is that it not possible to change the owner. Although this sounds bad, it doesn't pose any serious problems - as both owners and editors have the same (full) permissions. The only potential annoyance is that if you are not the owner, the report will be listed for you in the 'Shared with me' tab rather than the 'Owned by me' tab.
Even if a user shares a report with you and later you set that user to be 'inactive', the report will still be accessible to you. So there is no risk of losing reports should you ever need to boot someone out of your Google Ad Manager account (for example if an employee leaves the company).
I think things would be much clearer if Google referred to a report having a 'creator' rather than an 'owner'. The word 'owner' suggests special privileges - which is not the case. I would also like the ability to share a report from one Google Ad Manager account to another, in much the same way as you can already share a Segement from one Google Analytics account to another. They are all just configurations, after all.
Incidentally, should you ever want to change the owner of a report from user A to user B (to no real benefit), then this workaround might help you: