Be aware, though, the Adobe Acrobat Professional was originally written for use on Windows 2000 and XP, and trying to run it on a modern PC may result in all kinds of issues. We managed to set it up on a Windows 7 x64 system regardless, but you may not be so lucky, and installation is only the first potential problem area. Don't download the program unless you're willing to spend plenty of time trying to get it working.
If you're happy with Adobe Acrobat Professional, then first download the APRO23_Win_ESD1_WWEFG.exe executable. It's a chunky 478MB in size, so choose a computer with a fast internet connection.
The installer should run correctly on Windows 2000/ XP. If you're using anything later, though, you'll need to give it a little help. On our Windows 7 x64 PC, we right-clicked the file, selected Properties > Compatibility, checked "Run this program in compatibility mode" and selected "Windows XP (Service Pack 2)".
Choose your "Default application for viewing PDF". Adobe Acrobat Professional will set itself as the default viewer here, but because it's so old, that's almost certainly not a good idea. If it also offers "Adobe Reader 11" (or anything else, in fact), choose that and click Next.
You'll be asked for your registration details. Enter your name and (optionally) company, and use the serial number 1118-1414-1955-8737-8172-0350 . Click Next > Next.
The Setup Type screen then offers you option of running a Typical, Complete or Custom installation. We'd recommend you select Custom, to be absolutely sure what's happening. Click Next > Next and choose your required components, then click Next > Install to install them.
If you're installing Adobe Acrobat Professional on an x64 system then you may see an error complaining that "the file 'AdobePDF.dll' on Windows Vista CS-ROM is needed". Click "Browse" and you'll find it's not in the current folder. Go up a folder to AdobePDF, double-click AMD64, choose AdobePDF.dll, click Open > OK, and setup should now proceed to completion.
Download: Adobe Acrobat Professional 8.0