Windows – Shell extension to display thumbnails of PDF files

There's a tool from Sysinternals called streams.

This page describes how to use it. It doesn't add an option to the context menu, but does allow you to unblock a number of files at once.

I've also found this post which gives a registry file that will do the trick:

Windows Registry Editor Version 5.00
[HKEY_CLASSES_ROOT\*\shell\runas]
@="Take Ownership"
"NoWorkingDirectory"=""

[HKEY_CLASSES_ROOT\*\shell\runas\command]
@="cmd.exe /c takeown /f \"%1\" && icacls \"%1\" /grant administrators:F"
"IsolatedCommand"="cmd.exe /c takeown /f \"%1\" && icacls \"%1\" /grant administrators:F"

[HKEY_CLASSES_ROOT\Directory\shell\runas]
@="Take Ownership"
"NoWorkingDirectory"=""

[HKEY_CLASSES_ROOT\Directory\shell\runas\command]
@="cmd.exe /c takeown /f \"%1\" /r /d y && icacls \"%1\" /grant administrators:F /t"
"IsolatedCommand"="cmd.exe /c takeown /f \"%1\" /r /d y && icacls \"%1\" /grant administrators:F /t"

which is probably closer to what you want. Copy it into Notepad, save it as something.reg on your desktop, and double click to add it to your registry.

Only Adobe and Foxit (of those 5) have subpixel rendering. This is seen by zooming way in on the screenshot and seeing color fringing. This is because each pixel on an LCD display is made of 3 subpixels: red, green, and blue. These can provide extra resolution. Foxit maybe just doesn't have as good of a rendering method. Hinting could play a part.