Did you just stumble upon a download or a file on your computer that has a digital signature from Prolific Technology Inc.? If that's the case, please read on.
You will typically see Prolific Technology Inc. when double-clicking to run the file. The publisher name is then displayed as the "Verified publisher" in the UAC dialog as the screenshot shows:

You can view the additional details from the Prolific Technology Inc. digital signature with the following procedure:
Here's a screenshot of a file digitally signed by Prolific Technology Inc.:

As you can see in the screengrab above, the Windows OS reports that "This digital signature is OK". This implies that the file has been published by Prolific Technology Inc. and that the file has not been tampered with.
If you click the View Certificate button shown in the screencap above, you can see all the details of the certificate, such as when it was issued, who issued the certificate, how long it is valid, and so on. You can also examine the address for Prolific Technology Inc., such as the street name, city and country.
VeriSign Class 3 Code Signing 2010 CA has issued the Prolific Technology Inc. certificates. You can also see the details of the issuer by clicking the View Certificate button shown in the screengrab above.
These are the Prolific Technology Inc. files I've collected, thanks to the FreeFixer users.
| Detection Ratio | File Name |
|---|---|
| 0/55 | PL2303_Prolific_DriverInstaller_v1.9.0.exe |
| 0/55 | PL2303_Prolific_DriverInstaller_v1.10.0.exe |
The detection percentage is based on the fact that I have collected 110 scan results for the Prolific Technology Inc. files. 0 of these scan reports came up with some sort of detection. If you like, you can review the full details of the scan reports by examining the files listed above.
The analysis has been done on certificates with the following serial numbers: