Hi Nandeesh,
That type of stuff is generally safe to sign, at least in my experience. I would request copies of anything you sign for your own records and read everything closely before signing, of course. If you are concerned about them changing details on whatever you sign, then you should print it, sign it by hand, and scan it to make a pdf or jpeg that they cannot edit. Send them the pdf and keep your printed copy on file for however long the term is on the NDA.
The only one I'd be hesitant about is that Service Agreement. You are presumably setting up a job in Upwork with this client (because it would violate the terms of service if you went outside of the platform), so that Upwork job would act as the contract and Upwork offers you some protection that you otherwise would not have. Some clause in their Service Agreement could contradict Upwork and you just don't want any issues like that.
