[SalesForce] How to update all profiles with the same Custom Object Permissions

Standard Profiles come default with set User Permissions. User Profiles and their customizations are set based on the org type:

In Contact Manager, Group, and Professional Edition organizations, you can assign standard profiles to your users, but you can't view or edit the standard profiles or create custom profiles. In Enterprise, Unlimited, and Developer Edition organizations, you can use standard profiles, or create, edit, and delete custom profiles. For standard profiles, only certain settings can be changed.

Each standard or custom profile belongs to exactly one user license type.

Essentially, these profiles are set up and only some of them allow certain functionality. Not all of the profiles allow access to certain objects (specifically, profiles associated to Portals are very restrictive). This is just how the profiles are set up.

Why not use list views to do this?

1. create a list view on Profiles, filtering on the profiles you want to modify
2. add only the columns Read,Create,Edit,Delete,ViewAll and Modify All for the objects you want to assign (by searching on 'object permissions'
3. save the list view
4. tick the 'select all' checkbox at the top-left of the list view
5. check the 'modify all' checkbox on one of the records. The system will ask you if you want to apply the change on all selected profiles.