Enable PDF and EPUB build #555

Job	Run time
sync / sync	4m 32s
check / Build docs (latex)	6m 18s
check / Lint translations	37s
check / Build docs (html)	6m 17s
check / Check for zero-width space characters	5s
check / Build docs (epub)	5m 49s
check / Build docs (pdf)	12m 22s
	36m 0s

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