The company I work for is copying & pasting articles from PRweb onto the "news" section of our website. Does this affect search rankings at all?
The content is duplicate! Your website will definitely be penalized for using content from other sites.
It definitely affects your ranking on search engines. It also a waste of your time and effort because the owner can't get something financially in return. But, if the purpose of the task, copying and pasting articles, is not meant to generate income but for personal information purposes, then continue what you are told to do.
Your website's reputation will definitely fall down, unless and until you use fresh content for submissions.
It's duplicate content. It probably won't do any harm, but it certainly won't do any good either. And whatever you do, don't suggest they 'spin' it to make it unique. Spinning is dead, because all the major engines can now detect spun text. Hell, even we can detect it.
It will spell doom for your website. You can rewrite them or get in touch with experts to rewrite for you.