How can I copy and paste a slice into another Illustrator document or save it as a PDF?

I'm trying to tile a sewing pattern and am using the slice tool, but when I go to save the slices I can only figure out how to save them as PNGs or JPGs. When I save them this way the lines look a little distorted and I'd like them to look clean. If there's a way for me to save them as PDFs or copy and paste my slices into another document to be saved as PDFs that would be great. Any help with this is greatly appreciated!