ASP/VB Byte Arrays, Iframes, Parents, Children And Variables?

I have an aspx page which houses an iframe. When a button is clicked, a WCF is called to produce a PDF which is read into a byte array. I was storing the byte array in a Globals.vb file like this:

Public Shared PDF_Data as Byte()

The global was loaded from the parent aspx page like this:

PDF_Data = MyWCF.Create_PDF_File(SomeVariable)

After that, the iFrame's src was set to a blank aspx page, which had the following code in the page_load event:

'Write the PDF binary data to the screen (viewer)
Response.Clear()
Response.Buffer = True
Response.ContentType = "application/pdf"
Response.BinaryWrite(Globals.PDF_Data.ToArray)

However, realizing that this application will have several users who will get different PDF documents, I have learned that this is not the way to go. My shared variable would be accessible to all users, a big no-no.However, I am stumped as to how I'm going to store the byte array and make it available to a child aspx page from it's parent.