Just had a look through my Aerosoft account for a previous game I downloaded from them.
When you click download, and pay through the Aerosoft shop, I got given this
-- Download (GAME NAME HERE)_german.exe
--Download (GAME NAME HERE)_english.exe
---Download (GAMENAME HERE_truck.exe
I could download both the German and English version of the same game, as they were all on my download list. The truck was just a bonus vehicle thrown in for good measure.
There is also a Update link on the Aerosoft site to download extras from. This is called Support-Base, and requires another account (however it is purely for updates and therefore no payment details or address details are required...I dont why they can't be both on the same page but y'know).
Here you can download updates such as in this Game Update 1.1 and Flicker Removers, as of when they become available. One would assume that this is where the English Manual would be downloaded from when available!
So I would believe Aerosoft would place a English Manual link in the download list on the game page or your purchase history for easy download. Need any more help let me know, as I have experience with the site!