For slide-formatted pdf to ppt, I use a number of tools with varying results. Because the results are dependent on content -- as well as the initial setup of the ppt environment (backgrounds, etc.) -- I suggest you experiments with some of the free tools before moving on to the more costly solutions. For other than extracted slides ... I have not found an acceptable tool to automate the conversion of pdf files into PowerPoint. But I do use Pdf To Ppt Converter Professional to export graphics to individual files and to recognize text using OCR. Then I cut-and-paste the wanted copies into my PPT format. I do my footnotes as the last slide -- then I can use hand-outs, projected talk slides, or make the entire package available on the web.
I don't have as much time to work with each individual presentation, but it's not easy to put the PDF file into the correct format and the conversion doesn't always work. For example, the conversion of PPT slides into PowerPoint is more complicated (to my knowledge) than the conversion of the same files into JPG. But the general process still applies. After the import ... Now that the PPT has been imported, you should add your presentation as a slide under the slides box and start working. To get started, you should get a copy of the slides from a previous PPT. If the slides are well presented (without footnotes or handouts) you might just want to work on the summary at first -- it's easiest to do that in a separate file. I usually select the presentation from another format, such as PAYCHECK or DVI, or from a web.