To sign "the ghostscript driver" you just have to sign the INF-file that comes with Ghostscript.
There's an article on technet describing the steps required to do so.
The steps are:
1) Create/acquire a certificate
2) Ensure that your computer trusts the certificate (place it in your cert store if required)
3) Download and install the Windows Driver Kit (WDK)
4) Change the CatalogFile=oemprint.cat
in the INF file to ghostpdf.cat
5) Change the DriverVer=01/02/2007,1.0.0.1
to DriverVer=01/01/2013,1.0.0.1
(maybe you need some other date, you'll see that in the next step)
6) Use the Inf2Cat
tool to create a cat file (was at C:\Program Files (x86)\Windows Kits\8.0\bin\x86
for me):
NOTE
Use cmd.exe not powershell, as powershell gives Parameter format not correct.
error all the time
Command:
inf2cat.exe /driver:c:\path\to\folder\whereCatFileIsIn /os:7_X86,7_X64,8_X86,8_X64[,other OS you'd like to support]
7) Sign the cat file using the signtool
(Same directory as the Inf2Cat
tool)
Command:
SignTool.exe sign /f "C:Path\to\my.pfx" /t http://timestamp.verisign.com/scripts/timestamp.dll "C:\Path\To\ghostpdf.cat"
(See the signtool docs for more informations about the available paramters)