Let me know if you think other sites would benefit.
The last sentence is a little confusing:
If you're an academic, it's a great place to establish a reputation as an expert in the field, apply for funding and sponsorships, and network with other English professionals.
Is English Stack Exchange a good place to apply for funding and sponsorships? If you create a similar document for other Stack Exchange sites, I would suggest clarifying where such funding and sponsorship is available, as it would be of interest to many readers.
Second item: I'm unsure what an English professional is. We are English-language speakers, with varying degrees of proficiency, and of all nationalities. Some of the other Stack Exchange sites are specifically targeted to academicians or research-level experts e.g. Economics Stack Exchange (in public beta) and Mathematics (or maybe Mathematics SO, I don't recall). If you will be producing similarly themed pamphlets for other Stack Exchange sites, do confirm whether the site audience is in fact targeted toward that level of expertise.
Last item: The letterhead and colors were fantastic! I viewed as a PDF in Google Docs, directly in Adobe Acrobat and as a printout. It looked so pretty in all three!