How to Send pdf files from admin account to user accounts in my website?

You have other options like the Response.OutputStream.Write which will take an array of bytes if you have the pdf in the database.

In my case each user belongs to a group and using the group number I check the folder for a specific filename and create a list of a struct with a filename, filepath. On the page I create a repeater and render two columns one with a linkbutton with text="View" and the second column with the filename. On the repeater command I just do the code above and the command argument I set with the filepath; I use the argument from the command as the param fro WriteFile.

Actually, multiple pdfs may be sent to 1 user & each of them will have different names.  I will send those files one at a time by using dropdown box for selecting users & file uploader for selecting the pdf from my machine.

Are you saying that if I have all those multiple file names "same", my job would be easy?..

 response.WriteFile("FilePathGoes here");

remember to use Server.MapPath if you need