Download bot-gated PDFs via Wayback id

Problem

Many think-tank and publisher sites (taxpolicycenter.org, urban.org, SSRN delivery) serve an HTML bot-challenge page instead of the PDF to non-browser clients. A browser User-Agent header does not help. The downloaded "PDF" is actually HTML.

Context / Trigger Conditions

• curl -o file.pdf <url> succeeds but the file starts with <!DOC
• pypdf raises invalid pdf header: b'<!DOC' or PdfStreamError: Stream has ended unexpectedly
• Firecrawl scrape returns clean markdown for the same URL (its proxies get through), but Firecrawl does not return the binary — only parsed content

Solution

1. Request the file through the Wayback Machine's raw-content (id_) endpoint, which serves the original archived binary without rewriting:

   curl -sL -A "Mozilla/5.0 ... Chrome/126.0 Safari/537.36" \
     "https://web.archive.org/web/<YYYY>id_/<original-pdf-url>" -o out.pdf
   

   <YYYY> is any year likely to have a snapshot (e.g. publication year); Wayback redirects to the nearest capture. The id_ suffix after the timestamp is what requests the untouched original.
2. Verify the download with pypdf — a bot page fails immediately:

   from pypdf import PdfReader
   r = PdfReader("out.pdf"); print(len(r.pages), "pages")
   

3. If Wayback has no capture, fall back to: another mirror found via search (Exa/Firecrawl), or Firecrawl scrape for the parsed text when the binary is not strictly needed.

Verification

PdfReader opens the file and reports a plausible page count; first-page text matches the expected title.

Example

Verified 2026-07-15: taxpolicycenter.org/sites/default/files/publication/165884/ssrn-id4797771.pdf and urban.org/sites/default/files/publication/80621/2000790-...pdf both bot-gated to direct curl (with UA), both downloaded intact via https://web.archive.org/web/2024id_/<url> and .../web/2023id_/<url> (18 and 12 pages).

Notes

• Government data hosts (e.g. ticdata.treasury.gov) are usually NOT gated — try direct curl first; Wayback is the fallback, not the default.
• Wayback captures can be stale for frequently-revised documents; check the snapshot date if currency matters.
• See also: the pdf skill (parsing/extraction after download) and firecrawl:firecrawl-scrape (parsed markdown when the binary is unnecessary).