Create a new PDF document from what?
A PDF is the end product of the publication process - from a layout application such as Pagemaker or Quark, a graphics application such as Photoshop or Coreldraw, an office program such as Word or Excel etc. It's a way of retaining all the elements of the original publication in the format in which they were put together, and allowing another computer to view/print it in its orginal format.
What do you need to produce one? You need two things: a postscript printer driver to convert the original publication into postscript (a type of computer language), and an 'engine' to convert the postscript to a PDF. Acrobat Distiller can be both the 'printer' that makes the postscript and converts it to PDF.
Almost any postscript printer can do create the postscript file (go to File>Print, select a postscript printer from the menu. It can be a real physical printer, or it can be a 'virtual' printer i.e. all you need is the driver).
Creating the PDF from the postscript is a little bit trickier, although there are alternatives to Distiller e.g. Ghostscript.
Adobe dug themselves a bit of a hole and confused a lot of people no end with the naming conventions used for Acrobat. Some people mean just the Reader when they refer to Acrobat, others mean the 'full' program - which contains three programs: Distiller, Reader and a third one called Acrobat, which allows limited editing of the PDF.
So to answer your specific question: >>can I combine 4 pdf docs into one new one and include an xcell chart in this new document<<<
Yes. With the 'full' Acrobat, you can combine 4 PDFs into one. With Distiller, you can make a PDF of an Excel chart or worksheet, and combine that with other PDFs made from different sources e.g. a Word document.