If I download a document on to my computer that is a work product from one of Upwork's freelancers, is it safe in terms of bugs or other spyware that could compromise my computer or personal information?
Upwork has automated malware/virus filters that it applies to files processed through its system. But Upwork is not a cyber security company. Upwork offers no assurances about the safety of files that freelancers send you.
I can assure you that when it comes to files provided to you by freelancers you hire, they are almost certainly safe. But Upwork makes no guarantees whatsoever about those files being safe. That would be a matter between you and the freelancers you hire. Upwork is not a party to the contracts when you hire freelancers. Freelancers you hire through Upwork are not employees of Upwork.
If you want to hire consultants about file security and other digital security topics, you may hire such people on Upwork.