(phranque: content-disposition: attachment is meant to force a download - isn't it? Isn't that the problem salman is having already?)
Welcome aboard salman, if you are unable to VIEW them or they download automatically - it means either you don't have the plugin installed OR the server is not configured to serve .pdf's as PDF's (see first part of previous post.)
A corollary, if you have uploaded these pdf's in ASCII mode, they won't be viewable in any case. Make sure you upload PDF's in binary mode.
If you can VIEW the pdf file but want it "in the page" instead of "being the whole page" you will have to use an iframe or frames.
<iframe src="myfile.pdf" width="600" height="600">
(in frame-nav.html" below)
<a href="myfile.pdf" target="pdf-frame">
<frame src="frame-nav.html" name="frame-nav" id="frame-nav"/>
<frame src="pdfs-will-load-here.html" name="pdf-frame" id="pdf-frame"/>