What can I use instead of gnome-open?

You can use xdg-open to open documents, like so:

xdg-open mydoc.pdf

This has a bonus of being desktop agnostic so it should work regardless of what desktop the user has installed. In GNOME itself gnome-open has been replaced by gvfs-open.

References:

• xdg-open info page on portland.freedesktop.org
• What is the replacement for gnome-open in GNOME?
• xdf-open vs. exo-open

You can use gio too. For example gio open notes.doc.