No. The platform does not allow you to add another user to the account you have already established for your company.
If you would like a co-worker or employee to be able to use your account, you will need to share your login credentials with them (i.e., the email address and password used to access your account).
A co-worker, employee, etc. is welcome to set-up his or her own account with Purple Briefcase, but they will also need to request their own school connection(s). Job posts submitted by their account would be not be included in yours and vice versa. They will be separate accounts.
And finally, PowerConnect cannot be shared between multiple accounts, but as with non-PowerConnect accounts, you can share your login credentials (as described above) so others in your company can submit job postings by using your account.