I purchased Movie Studio Platinum 17 through Steam, and I don't think a PDF version of the manual is among the files downloaded. Is the PDF available somewhere?
When purchasing from Magix the manual pdf download becomes available from your Magix account. But Steam purchases don't come under the Magix customer database as Steam has its own client system. So I suspect you need to ask Steam.
Most (if not all) of the text in the PDF manual may be found in the program's Help menu > Content (assuming the Steam was allowed to include it in their version).
There are also several tutorials available, e.g. here and a 300-page paperback Guide here.