I've found a moderately priced Tamron 70-300mm f/4-5.6 di ld macro for Pentax and I was thinking about getting it to use it with my A7. Does anyone know if I can control the aperture manually on the Pentax version?

There's a section about it on this PDF http://www.tamron-usa.com/assets/pdfs/A17.pdf ...but I didn't find it very clear.