After several weeks of searching for a solution for the iPad "virtual PDF printer" on several internet forums I will give up.
Thanks also to Jpmboy for all effort to help us find it.
AppRey support answered: Thanks for interesting in our app, Apple don't allow us to use their AirPrint feature.
It looks that Apple allow the use of AirPrint ONLY for hardware printers like hp, canon, brother etc.
I finally have got the advice to try Save2PDF from EuroSmartz.
The Save2PDF app is NOT a "virtual PDF printer", but it make it possible to create PDF files in an odd way (compared to the easy methods in windows).
I have so far tested to create PDF files with Save2PDF from both secure (https://) and unsecure (http://) web sites.
Save2PDF has its own web browser and I suggest you to use this instead of Safari on the iPad if you want to print (save) to PDF files. The Save2PDF browser has a "PDF" button.
In Safari, if there is a "print button" inside the web application, for example a bank account or a time table, the "print button" will not work.
When you touch the "print button" the iPad will show you some dialogs to choose printer, then searching for printers, and finally "No AirPrint compatible printers found ...."
Instead of touching the "print button" you must edit the URL field and put the letter "z" in front of https:// (like zhttps://) or in front of http:// (like zhttp://)
If you use this editing of the URL in Safari it will open up the Save2PDF browser and you can choose to preview the page(s) you want to print (save) to PDF.
However, if the web page is a https:// site you will be thrown out from your login and must login once again in the Save2PDF browser.
That is why I suggest you to use the Save2PDF browser instead of Safari. You can set up (or import) favorites also in the Save2PDF browser. And also use the "PDF" button!
The Safari browser is a little bit like an application without facilities. No printing, no flash support and so on.
Save2PDF is NOT an optimal solution, but it will at least give you the opportunity to use the iPad as a business tool and not only as a toy.