Yes, you can crawl multiple sites in the same Crawlbot job: simply add each seed URL, separated by a space, when creating or editing your job. Crawlbot will then apply any crawling and processing patterns (and/or regular expressions) to all of the domains/subdomains contained in your seeds.
Extracted content will be indexed in the same Crawlbot collection; you can use a Search API query to filter by site (
query=site:diffbot.com) if you’d like to narrow results after crawling.
There is no hard limit to the number of seed URLs.