Instead of using session I would suggest you to use QueryString only. Just have a look below:
In Page 1:
Response.Redirect("~/PrintBilledReport.aspx?sentence="+s+"&word="+s1+"&letter"+s3);
In Page 2:
string s1 = Request.QueryString["sentence"];
string s2 = Request.QueryString["word"];
string s3 = Request.QueryString["letter"];
Now you can use the string variables in 2nd page.
--Amit