You need to have execute permission to enter the `/home/user1/` folder and any subfolders in it, or to access any files in it.

By default linux sets user home folder to `750`, or `rwxr-x---`, meaning users which are not owner of the folder or in the group that owns the folder are not allowed to enter that folder.

It is not enough to have permissions to the subfolder or a files inside user1 home directory you also need to have permission to enter/passthrough that directory to get to objects inside it.

Execute permission on a file gives you permission to run the file it it is a script or an application, execute permission on a directory gives you permission to enter that directory or pass through it to get to files and folders inside it.

You can either put `user2` in a group that owner `/home/user1`, or use `setfacl` command to set additional permission to give execute permission to just `user2` on `/home/user1` so that he can enter the folder to get to `/home/user1/Documents`

something like this would give execute permission to user2 on /home/user1

    setfacl -m user2:x /home/user1/

You can then use `getfacl` command to see acl rules on the folder

    getfacl /home/user1

For directories read permission means that the user may see the contents of a directory. Write permission means that a user may create files or folders in the 
directory. Execute permission means that the user may enter the directory.