First rotate the drawing:
1. Hold 'Ctrl' and press 'A' to select all the objects
2. Enter "ro" in command line ('rotate')
3. Specify base point to (0,0), enter "0,0" (you can also click on anywhere you'd like to specify)
4. Enter the rotation angle, i.e 90 degrees, and press enter
5. You can try zoom extents to see the whole drawing.

Then about to edit the drawing:
If you are converting a PDF into DWG, when you say you are going to edit it, is the drawing converted into an image? What command do you want to use to edit the drawing?

I don't know which tool you are using to convert PDF to DWG, but I'm using AutoDWG PDF to DWG converter and there is no need to rotate after conversion, you can also find it can convert images in PDF's into editable lines, arcs. If your PDF is a raster PDF file, you can send it to me (ameriewhite at gmail), and I will convert it into vector drawing and send back to you. 

Edited by AmerieWhite - 25.Jun.2009 at 03:31