Can SortSite check pages by domain? – Yes. The tool allows you to literally browse to any website using the software and then crawl the entire site looking for issues. (even sites that aren’t under your own domain)
Is there a limit on the number of pages you can check in batch? – 22,000 pages is the limit (see link above)
Does it look at docs/pdfs, or just HTML? – The tool scans all documents that it can crawl to (as long as they are linked to on the website it will be scanned)
Does it check for outdated code or just accessibility type problems (missing alt tags, no language, etc.)? – Accessibility issues as well as broken links & spelling, browser compatibility.