Learn French: Il est indispensable de lire la totalité des documents. - It is essential to read the entirety of the documents.

Yes, you could say de lire tous les documents (to read all the documents). Using la totalité des (the entirety of the) is a bit more formal and emphasizes reading every single part of them, but the overall meaning is the same.

If I wanted to replace les documents with a pronoun to say 'read them all', how would I use tous?

You would say Il est indispensable de les lire tous. Because tous is acting as a pronoun here meaning 'all of them', it follows the rule from this lesson: you must pronounce its final 's' so it sounds like 'toos'.

Why is there a de between indispensable and lire?

The impersonal structure il est + adjective requires the preposition de before an infinitive verb. So, il est indispensable de is the standard grammatical way to say 'it is essential to'.

Why does it say des documents instead of de documents after totalité?