Can I edit with a friend on a free plan?

On a personal project, which is any project outside a workspace, Share lets you add people by email as guests. A guest can open the project, read everything and leave comments, and the row shows Guest · can comment; there is no edit option to pick. You can also turn on Anyone with the link as Can view or Can comment (commenting needs a login). This is the same on Free and Pro.

A guest cannot change anything and cannot make their own copy of the project. If your friend wants to build on your work, export it or ask them to start their own project.

To edit together

Co-editing is part of Studio. Create a workspace, move the project into it, and invite your friend with Can edit; that makes them a workspace member and uses one seat. Both of you then work in the project at the same time, with live cursors, field locks and comments.