fail to open pdf in IE

[Milk]

I use Vista Home and everytime I click on a pdf link in the website, a warning message says it's probably not an effective digital signature and ask if I will allow or deny the operation. 

Even I click on allow, I can't open the pdf.  I suspect it's related to some security setting in IE but I just don't know how to fix it.

[Broni]

Download, and install FoxIt: http://www.filehippo.com/download_foxit/

[US]

I have a similar problem I'm running Xp Pro on a pc
When I click on a PDF file the XP Dialog Box Opens
to show the download. Then Adobe Reader 9.0.0 opens
with an error message right in the middle.
"There was an error opening this document. This file cannot be found"

Well I know it is not just this document.

If I download it to the desktop I can click it and open it from there,
but for me that a little bit of a hassle. I have tried reinstalling Adobe reader and that didn't change anything. Any ideas

[Helpmeh]

Wait, just to double check, save the PDF to your Desktop, then drag it to IE.

[Broni]

IE won't open pdf file, unless it has Acrobat Reader plug-in installed, and Adobe sucks.