Go to your library, select the game, and look under the "Extras" or "Goodies" section. GOG Galaxy Client: Select the game, click More > Extras .
Once you purchase the game on GOG.com , you can access these files through: heroes-of-might-and-magic-3-complete-edition-gog
Sometimes a Manuals or Documents folder is created within the game directory (e.g., C:\GOG Games\HoMM 3 Complete ) during installation. Go to your library, select the game, and
A quick-reference PDF for new players. Soundtrack: High-quality audio files of the game's music. Where to Find Them A quick-reference PDF for new players
Instead, GOG provides the original "paper" contents as that can be downloaded alongside the game: Manuals: A comprehensive 209-page digital PDF manual. Creature Tables: Reference charts for unit stats.
The edition on GOG.com is a digital-only release and does not include physical paper materials.
If you are looking for the materials, you would need to find a vintage "Big Box" copy or a 2002 retail "Complete" edition from secondary markets like eBay or specialized collectors' groups. Physical copy of Heroes of Might and Magic 3 exists