I hardly understand your question. What do you mean by information? Is it a file, a page, an abstract piece of data? What do you mean by client? Is it a browser, a computer identified by an IP, a registered customer?
The case of the registered customer is the easiest one. When downloading a file or loading a page or whatsoever, you can save a record in a table, saying that the customer A have requested the piece of data B. There are some nuances, especially with files download, but I'll not bother you with the details, especially since it's off-topic and would be more appropriate on StackOverflow.
If on the other hand you want to track downloads from the same machine, you can do it by identifying it through the IP address. This has some difficulties too: the same person using the same device can change IP even during the same session, or multiple devices can share the same IP address (like two computers of the same company connected through the same router).
Finally, you can track the client through the cookies. This has two weaknesses: the person can at any moment delete or change the cookie (and somebody else can use the same cookie), and if the person changes the browser, cookies will be lost.
Depending on your precise problem, you can choose one, two or all three types of tracking to be able to know more or less who downloaded what.