Keep in mind that any ISSUU downloader can only scrape the images in the ISSUU viewer.
For this reason you always get re-compressed JPG's and it's not ideal for everything.
There are several sites like the one above, for ripping these images. I think one of the smoothest/best is probably: [Login to see the link]
That site also supports a couple other content-publishing platforms like Calameo & Yumpu.
Because none of these tools properly set page size, the first thing I do, is to open the PDF in an editor and customize the page size to crop the white borders. This is a huge help to creating a more professional PDF that appears like the original 🙂