Daniel 12:4 But you, Daniel, shut up the words and seal the book, until the time of the end. Many shall run to and fro, and knowledge shall increase.

Because the second sentence is listed with the first sentence in this verse it is implied that those two events are indicators of an end.

The original text was not numbered and they are two separate sentences. The revisionist tied those sentences together by implication by numbering them together.

It is true that the world is running to and fro and that knowledge is increasing right now. 

Daniel is the most prolific prophet in history both in content and accuracy. We tend to believe what he has said will come true.

What book did Daniel have access to and was allowed to seal?

The word “until” implies that Daniel is going to be available to unseal that book.

The end of what?

Implications do not answer questions. They only create more questions.