Error message : "That assembly does not allow partially trusted callers. "

When i go to admin section and go to SalesTabe> Orders
And View Specific Order and whenever i try to click on the button " Invoice PDF"
i get a message : "That assembly does not allow partially trusted callers. "
Why ? because when this nopCommerce project is running on the localhost i don't get any error message like this
I am getting this message when i try to run the project on the server
what's the solution for this kind of problem ?

PDF and Excel options are not supported in medium trust

Where can you change the trust level?

"PDF and Excel options are not supported in medium trust"

first of all what is the meaning of medium trust ?
and my question was that in admin section i cannot access the pdf invoice, if there is some access limits in admin section then who has got the full access ?
admin should be able to have access of everything.
In order to view invoice pdf and excel files what should be done and how ? please explain the procedure ?

You cannot change your trust level. You hosting provider does it.

You can find more info about medium trust here

So if there is an order that has been placed on the website, and the admin wants to get the invoice of the order to wants to print the pdf version of order then there is no way to do that ?
I mean how is it possible that there is no way to print the invoice of the order ?

any suggestions please...

You can move to another hosting

1) sorry but could you please elaborate your answer, what exactly you mean by move to another hosting ?
you mean i have to move the website from 1 server to another ?
2) what are the things to keep in mind while launching the website  on the server in order to avoid this (Error message : "That assembly does not allow partially trusted callers. ")
4) Is this trust level depend on the hosting party? i mean different hosting party have different level of trust ?
3) Please explain me everything in details, i am new in this technology

What's meant by moving to a different host is:

Search different hosts and pick one that allows full trust.

Preferably one that only offers Windows hostng.

The ones that offer both Windows / Linux are the ones that often (with some exceptions) give advise which do not make any sense from me looking at some of the posts in this newsgroup.

If they do offer full trust hosting, they usually list that somewhere in what they offer.