As a PhD Physicist, a deep knowledge of Latex is necessary.
I have written many essays, a few thesis', and require the extra work.
I have a working knowledge of physical principles, so can spot mistakes if necessary, as well as maths and some chemistry. The depth of knowledge of the subject is dependant on the particular job.
I also have a working knowledge of Adobe illustrator, carrara daz (for 3D modelling), Adobe photoshop. This must be mentioned if the job requires use of these programmes.
Additional services I could provide are graphing (if data is given as txt), Bibtex organisation, 3D plotting in Matlab if necessary. I use several programmes to graph.