In Daniel chapters eleven and twelve, a heavenly being revealed the future of Israel to Daniel, but then the heavenly being speaking to the prophet, told him to shut up the words and to seal the book until the time of the end. The heavenly being said further,
“…many shall run to and fro, and knowledge increase” (Daniel 12:4).
Many running to and fro does not refer to worldwide travel of our day or some future day, but keeping it in context, many things were going to be happening (remember chapter 11?), to bring about the fulfillment of these messages from the Lord in the Book of Daniel.
It was as though the heavenly being told the prophet, “Daniel, sit back and complete your writing. Do not worry about things. There is going to be plenty of activity, both in front of the curtain and behind, but it is the Lord’s doing.”
Knowledge increasing does not refer to what we call “The Information Age,” but knowledge concerning Daniel’s prophecy shall increase as events unfold, which has happened. We open the history books and see Daniel’s prophecies fulfilled clearly.
Therefore, Daniel could not by any effort, increase his knowledge of the things that he wrote in his prophecy, or in the rest of his book.
Some things he could understand after seeing them fulfilled, which is the same way others could understand them. Daniel saw Persia take over Babylon. Beyond that he could not figure out his prophecies.