You can invite someone to join your team. The PDF and Submissions are shared by team members (under permission controls as described below). As the sign-up user, you can join as many teams as you are invited. Press your name in the main menu, you can switch to a different team in its popup menu.
For every PDF, you can manage who is the Form Editor, Form Submitter or Form Submission Viewer. To open this permission popup, go to
Dashboard, mouse over and highlight the targeting PDF, then click the right-top
gear icon. In dropdown menu, click the “Permission” item.