Some of these files are very much nonstandard, even when the standard leaves no leeway (unlike HTML). E.g., every PDF standard requires an %%EOF, startxref offset, and an xref table (or an xref stream in the later versions), but this PDF file is missing those, among other oddities, like the page object missing a /Type and /MediaBox. Too bad the author doesn't specify which implementation these are supposed to work in.