In that case, please do the following:
1. Open a PDF document with Adobe Reader or Adobe Acrobat
2. Click File > Print...
3. At the top of the Print window, select your printer and click Properties
4. Select A4 paper size and click OK
5. On the Print window, click on the Multiple button
6. Select 2 pages per sheet. Optionally, you can select to print page border
7. Select Portrait as orientation
8. Before printing, you can see the print preview window on the right. If it looks good, you can go ahead and start printing
Let me know if this is how you wanted to print your PDF documents.