Enable PDF and EPUB build #557

Job	Run time
sync / sync	4m 9s
check / Build docs (latex)	5m 57s
check / Build docs (html)	5m 49s
check / Lint translations	43s
check / Build docs (epub)	5m 26s
check / Check for zero-width space characters	5s
check / Build docs (pdf)	5s
	22m 14s

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