If i have some pdf's loaded into my site (without pdftohtml enabled) and i decide to set-up the search facility (document content searching as well) will i have to re-add the pdf's with pdftohtml enabled so that they are indexed and available to the search?
No, you can just trigger a site-wide reindex via the Search Manager. This will then run pdftohtml over any PDF assets that are loaded.
However, PDF contents are not automatically searchable. You need to use the Keyword Extraction pop-up on the metadata page to insert the keywords found by pdftohtml into an indexed metadata field (e.g. a "Keywords" field). Only then are the keywords actually searchable.
Actually, PDF files index their contents in the same way as standard page - if pdftohtml is installed. They should come up in an include_all field.
Really? You learn something new every day! Does this happen with MS Word documents as well?
It sure does.