Can people upload a photo or document through my Form Builder form?

Yes. Add a File Upload field:

1. In Contact Forms, click the pencil icon (Edit fields) on the form.
2. Click the + button and choose File Upload from the Common fields, then Apply.
3. Set its Label in Field Settings, tick Required field if needed, and click Publish.

When someone picks a file, it is uploaded straight away and the submission stores a link to it. Open the submission under the form's Submissions tab to view the file.