SINCE angels do have language and their language is one of words, they also have written materials; and through those written materials just as through their conversation, they express what their minds are sensing. I have sometimes been sent pages covered with writing, just like pages handwritten or printed and published in our world. I could even read them in much the same way, but I was not allowed to get more out of them than a bit of meaning here and there. This was because it is not in keeping with the divine design to be taught by written materials from heaven, but [only] by the Word, since this is the sole means of communication and union between heaven and earth, and therefore between the Lord and humanity.
We gather from Ezekiel that pages written in heaven appeared to the prophets as well:
When I looked, behold, a hand was stretched out to me by the spirit, and in it the scroll of a book that he unrolled in my sight. It was written on the front and on the back. (Ezekiel 2:9–10)
And in John,
I saw in the right hand of the one who was sitting on the throne a book written within and on the back, sealed with seven seals. (Revelation 5:1)
The occurrence of written materials in the heavens is provided by the Lord for the sake of the Word, for in its essence the Word is the divine truth from which both angels and people on earth get all their wisdom. It has in fact been spoken by the Lord, and what is spoken by the Lord passes through all the heavens in sequence and comes to rest with us. In this way it is adapted both to the wisdom that angels enjoy and to the intelligence that we do. As a result, angels have a Word that they read just as much as we do ours. They draw their doctrinal principles from it, and their sermons come from it (Section 221). It is the same Word; but its natural meaning, which to us is its literal meaning, does not exist in heaven. There is a spiritual meaning there instead, which is its inner meaning. The nature of this meaning may be seen in the booklet The White Horse Described in the Book of Revelation.
from Heaven and Hell, Section 258, 259
Section 221: Published 12/16/2016