I don't know the "best" way.
Here are 2 ways that'll get 'er done, maybe inefficient.
1) Convert using one of the free web converters, like
zamzar
Resulting .doc should be freely editable.
2) If you have an OCR program, scan the documents by optical character recognition, and send the result to Word, then edit. It should be able to scan directly from the file on your computer without needing a paper printout or a flatbed scanner.
2a) If you have a screen image program, like Snagit, you can scan the .psdf image into an image format like .jpg or .tif, then OCR on that.
You mention .doc so I take it you may not have Office 2007.
In case you do have Office 2007 Pro, then you have OCR capability built into that, as Office Tools / Microsoft Document Scanning. That feature may not have been activated on your installation by default, but you can go into Control Panel / Add or Remove Programs and Change your Office installation to activate it. I don't know if previous Office editions have this.