I don't think you are quite following @Colin's logic or understanding why PDF is a bad idea here. As I said in a previous post, Make a PDF file - #3 by drmibell, PDF is a document format, and (with perhaps a very minor exception) it cannot be read or written except as a complete file. @Colin is advising you to save ALL your data and write it as a complete file file for each update. In general, you cannot simply append to a PDF file. Alternatively, you could read the file, extract the content you want, add the new content, and write out the new file. Either way, it's a lot of effort, and I don't see why you would want to do it often.
[EDIT] Apologies for getting "cross-threaded." I just noticed the more recent postings.
