This page offers Instruction scans for all Generation One (G1) Transformers released in America and Europe (below).
Scans from Japan and other lines (G2, Beast Wars, etc) can be found here.
Eternal thanks to James Wilson, the original curator of the Transfomers G1 Instruction Scan Archive.

Autobots
Decepticons

Historical contributors to the Instruction Scan Archive: Crazysteve, Devvi, Dr_Nilkog, EwOkSlaYer, Hatch, Hex, Iacon, Jack Lawrence, James Findley, James Wilson, Jarrod Trout, Jason Bell, Jeff Morris, Jeroen Blok, Jim Huey Lee, Kenny McCoy, Kranix2000, Kris Shaw, Matt Anderson, Michael Hofle, Mirage, Napjr, Neil Papworth, Palmeiro, Prime Saber, Primex15, Rapido, Richard C. Mistron, Risk, Rob Rocca, Scott Mangini, Senex Prime, Sonicjay, Steve Taylor, Tec, Tikgnat, Wayne Bickley, William Leijten and Zobovor.