A superior digital rulebook allows you to extract only your Legion. Print just the 6 pages for the Raven Guard. Print just the Wargear section. Better yet, a "rules compendium" PDF that sorts units by unit type (Infantry, Vehicle, Monster) rather than by Legion allegiance is vastly superior for list-building.
If you're looking for a specific PDF with 20 rules, could you provide more context or information about where you found the reference to it? horus heresy 20 rules pdf better
Games Workshop provides several free downloads to support units that aren't in the main "Liber" books. Legacies of the Age of Darkness A superior digital rulebook allows you to extract