> Do not generate PDFs “by hand”! You risk inadvertently generating PDFs that do not fully conform to the spec, and not noticing it because PDF readers are quit

> Do not generate PDFs “by hand”! You risk inadvertently generating PDFs that do not fully conform to the spec, and not noticing it because PDF readers are quite lenient in what they accept. We have that with websites too. Sometimes it is even hard to spot an error like a missing tag because browsers just assume (often correctly) that it was missing in the first place. But yes, probably also a reason nobody wants to write new browser engines.