I've been working on a project where I am dynamically filling form fields on a PDF using the PDFToolkit from ActivePDF. It's been great, with one exception.
The customer had created their PDF and sent it to me to actually put the PDF form fields on it. When they sent their base document, it was 35K. I noticed that when I opened it, made my changes and saved it, it was 279K, almost 8x larger, even if I made a change and then used "undo", effective making no changes.
Google to the rescue. I found this
article on PDFs, which explained why. The gist of it: always use "Save As" when saving a final version PDF. If you don't, it saves all your changes as a part of the document by appending them, increasing the PDF file size.
The thing that was killing my file size the most, though, was using a non-Base 14 font. I was using Times New Roman. By switching to Times Roman, the file size dropped to 36K. Quite a difference. Strangely enough, even though I didn't have the font embedded in the doc (the optimizer didn't pick it up and show it as on option to un-embed), it was the difference in my file sizes.
Lesson learned!