Nothwithstanding that VB6 is long dead, you can use the VB6 "Web Browser Control" in Shdocvw.dll to display PDFs. Or you could embed PDFViewer.dll from Adobe Reader if you have it.
As to getting the data from the database - we can't really help without details of the database and how you have stored the binary data, but I will say that you need to ensure that you write the raw
binary data to the file i.e. don't use a "text" file
Open YourFilename For Binary Access Write
That's about as much as I can remember, I haven't had a VB6 install for nearly 20 years at home. This would all be a lot easier if you ditched VB6 (after all, Microsoft have) and used a more modern (e.g. .NET based) language