Returns the PDF document for the invoice specified by the invoice number, including a cancelled invoice or credit memo. The response body is the PDF bytes.
The PDF is returned decompressed by default. It is only gzip-compressed when the request advertises Accept-Encoding: gzip, in which case the response carries Content-Encoding: gzip with a Content-Length for the compressed bytes and must be decoded as a standard Content-Encoding: gzip body. HTTP clients whose stack negotiates the encoding automatically also decode it automatically; a client that sets the header by hand may instead receive the raw gzip bytes (for example curl decodes only with --compressed). Omit Accept-Encoding (or send identity) to always receive the decompressed PDF. A very large invoice may exceed the decompressed-response size limit and respond with 500; request it with Accept-Encoding: gzip to stream the compressed bytes without that limit.
A 404 is returned both when no invoice with the given number exists for the authenticated tenant and when the invoice exists but has no PDF document available.