Don't bank on it.
Sometimes they do request further evidence but that tends to be for other conditions with a higher risk rating. A request for further evidence is likely to significantly prolong a date for assessment as well.
As you have your date it is likely that they have it already or did not request it (this isn't necessarily a bad thing so don't worry).
People really do get hung up on evidence but so much of it such poor quality (eg, from GP, Mrs X has A,B,F,H conditions). That is 99% unhelpful, maybe I have 3 of these conditions but it is affecting Mrs X very differently to me.
A valuable document is one which covers each activity of daily living, and a list of medications of you are feeling generous, written by a professional on headed paper and dated. That's pretty much it.
Professional letters of support are ££ and very low priority for NHS staff.
If you are going to ask for one, please have the courtesy to ask your GP, CPN specialist nurse first, otherwise they put the phone down on is in case we are trying to illicit obtain your medical info. And I support them 100% with that
This is my personal perspective: please think twice about including personal stories about what led to your PTSD/depression. We do not need them, it is not our business and we won't put it in report (likely euphemism as "traumatic event"). Assessors have awful things happen with subsequent MH effects just like anyone in the UK. It can be very triggering with details and photos.
You do not have to justify your MH problems.
On that note, photos of letters can be very helpful. Photos of ANYTHING to do with your body are not required. I believe you have a rash. I have no desire to see any intimate pictures or pictures of deceased people.
The assessors are not robots, they are people. People who have just read the latest awful story of the causes of PTSD for the fourth time that morning and then come across a distressing photo. I've known now more than a few just put the laptop lid down and walk away from the job because of that.
Please, do seek help, support and therapy, but not from the assessor. It's not their role and they do not present themselves as such and they are healthcare professionals and not counsellors.
Best of luck OP.