Website footprinting
Website reconnaissance: download, crawl, or scrape it, manually inspect it. Download documents from the site if any, or from known platforms, and use, for example, FOCA (Fingerprinting Organizations with Collected Archives) to scan them to collect the hidden metadata.
Resources
Fingerprinting Organizations with Collected Archives (FOCA) is a tool to mine documents for metadata and other hidden information (Windows-only).
Dirb, already installed on Kali, to brute-force find sensitive files.