from your original message:
For some reason one one of my shares most of my users are getting an “you need permission to perform this action” when trying to write a file or folder to it.
Creating a new file or folder on your share would need the proper permissions on the /common directory itself - I should have given you “ls -ld /common” as a command to just show those permissions.
Are you basically familiar with access permissions? The basic ones (as seen by “ls -l[d]”) come as three groups of “rwx” - telling whether the file/directory owning user, group or anyone else has either “read”, “write” or “execute” permission. (In case of directories, “w” means add/remove entries to that dir, “read” means you can actually search the directory for entries, and “execute” allows to access an entry if you specifically know it’s name - so you don’t need “r” if you already know the entry’s name.) If there’s a “+” behind these groups, extended access control lists (ACLs) are set, so you neeed to use “getfacl” to see the actual permissions.
So if /common is owned by “root” and group “Admin” and you’d have “rwxr-xr-x” as permission, only the root user can modify that directory anyone else may just look at/for entries.
You probably will want to set ACLs for /common that allow modifying access to /common for the groups you named in smb.conf.
Please note that this only applies to directory entries - even if /common had rwxrwxrwx (giving full acces to anyone), the file /common/20140306155821376.pdf would still only be writeable by the root user (rwxr–r–)!