How to check your Windows:
Keep the "Install Microsoft Office add-ins" box checked for seamless PDF creation from within Office apps.
Search for NitroPDF_Pro_9.5.x.x_x64.msi or the x86 equivalent. Verify the file size (typically 110-120 MB) and check for a digital signature from "Nitro Software, Inc."
: Locate the downloaded installer file and double-click to run it. If prompted by User Account Control, click Yes to allow the installer to make changes.
Comprehensive Guide to Nitro Pro 9.5.1.5 Final x86/x64 Installation