How to acknowledge oneself as the author of materials created in industry research position?
You should be able to place your authorship somewhere in the front-matter of the document without compromising branding.  I think the magic phrase you need is something along the lines of "Prepared by: [authors]".  

To take one of your examples: in a manual, after the cover there is often a set of front-matter with history and disclaimers and such.  You can add "Prepared by" as its own little subsection or insert it into the version and history information.  This makes it absolutely clear that you are the author, without putting yourself in front of the company's brand.