This is aimed squarely at the SoFoBoMo crowd but should be useful for others putting together pdf books for the web. I know several will be using Scribus as their layout software.
I'm using Scribus as my layout software, as I have done in the past. Normally when I'm playing around with layouts, I export a partial book to pdf to see how it stacks up. Last night I made a minor error in the options I chose and felt it worth pointing it out.
There is an important option in the pdf output dialog (below) where the type of image embedded can be selected. I accidentally chose "Automatic". Running a layout with just 10 images in it gave me a 7MB pdf file, even using the "medium" compression setting. I then re-ran the export but with jpeg selected, suddenly the same material was only 1MB. An issue to note. I don't know what image format Scribus chose under "Automatic" but it clearly wasn't as compact as jpeg. Visually there was nothing different in the output.
It might be that other pdf generating software has similar options around the format for image embedding, I don't know as I don't have access to other options. If anyone else knows of similar options in other software, post a comment.