no once you convert it to PDF you can not edit it
Some software can edit PDF to the extent of like MS paint can do.
And some even do highend prepress editting like trapping, color correction, masking (?, pls confirm)...pero ito na ang future expectations ng adode sa PDF...and its slowly becoming true...
expect to see almost all design softwares utilizing PDF's (at least ability to export it...sooner or later ability to edit like photoshop!)