Direct conversion is not possible, but you can do it with the help of two applications. Firstly, you need an application that is capable of opening HLP files and have built-in Print support. For that, Help Explorer Viewer is a suitable application. Download it through the link below. Secondly, you need a PDF virtual printer. CutePDF Writer is a good tool for this purpose. Download and install it from its official website listed below.
- Open Help Explorer Viewer and go to File > Open. Browse to where the HLP file is located and open it.
- Press Print and wait for the Print menu to open.
- Select CutePDF Writer and then press Print again. You will be prompted to save the file to PDF.