Using a Word Processor at A LevelWatch this thread
In terms of general marking- you won't be marked unfairly. If your work is identical to something written, then it will be marked the same.
The way I dealt with graphs was to draw the graph on the paper whenever it was needed (and I usually dealt with equations on paper) and then referenced, on the document, some sort of index on the paper (i.e. if it's question 5) c), then "Look at Figure 1 5.c). That sort of thing.
Other than that, all the usual writing/etc can go in the document. You just have to tell them where to look.
In terms of "forgetting to include," this did happen to me actually. One of my physics papers came back as an A instead of an A*- 2-3 months later I randomly got a letter saying they didn't mark my Paper 3 correctly because they'd lost some sheets from it (that went together with the word processed document that I'd written.) Clearly those sheets mattered a lot- my grade for that exam shot up 40-50%, which got me the A* I wanted. I already had A*A*A so I didn't need this, but it got me A*A*A*. Clearly for some however, it could make the difference between AAA and A*AA, something needed for a lot of top Uni's/etc.
I'm sure it's rare (my teacher had never seen this happen- granted not many people used a word processor anyway, but yeah.) It can happen. It's a risk in general, but you can always appeal your grade if you feel you've been marked unfairly (and request the paper back, which would obviously show any egregious errors like this.)
My best advice would be to just mark your graphs explicitly, telling them where to look. If your mark is less than what you expected (B instead of A, for example) then complain and ask them if it's been fully marked/etc, just to verify that they didn't lose anything. I might just be a bad example case, but the fact they lost 40-50% of my grade on that paper 3 was pretty ****y of them- the fact I didn't mind it too much was on me, though.