Have not tried this on the SL-6000, it does work on the SL-5000.
It allows you to add any document to your documents tab.

Licence: Proprietary
Works in 640×480: Unknown
Download: addoc_0.1-20020819_arm.ipk
IPK Information:

Package: addoc
Installed-Size: 2976
Version: 0.1-20020819
Depends:
Provides:
Conflicts:
Priority: optional
Package: addoc
Section: applications
Maintainer: Thomas Stephens
Architecture: arm
License: GPL
Filename: addoc_0.1-20020819_arm.ipk
Size: 3139
MD5Sum: 61bee8f03fed551202536e969ef3b14e
Description: Add files to Documents from the commandline
This lets you add files to your Documents tab from the command line.

If your shell supports wildcards, this application
can add more than one file at a time.