My goal is to have a set of hotkeys that paste the contents of ~/.paste1 through ~/.paste9 (each a plain text file), depending on which hotkey is pressed.

injecting keys

Regardless of the hotkey-trigger mechanism, The way to insert the text is to create a ~/bin/pasteme script containing:

And then put at the top of ~/.paste1:

And chmod+x it.

That seems over-the-top, huh? Unfortunately, most of the obvious/easy ways end up stripping newlines off the end of the file.

hotkey triggers

There are various ways to do this.

In Ubuntu Unity, press the Super key, search for "keyboard", and run the keyboard app. Go to the Shortcuts tab, click on the 'Custom Shortcuts' item, and add 9 entries there.