I actually make all my pages for print first at A5 300dpi print size, then I shrink it all down and spread the panels out vertically a bit. This is also how Shazleen Khan makes Buuza! Which is how her printed books look so good. She goes even further and rather than just spacing them out, she plays with the size, placement and shape of her panels too.
Redoing all the speech bubbles is necessary of course, because they can be smaller with smaller text compared to the art in print, and the placement will change with the new layout.
If you've made the art at web size, unfortunately it's just not going to print nicely, so if you have any desire to do a printed book in the future, you should be making all your pages at around 300, 350 or even 600dpi and then shrinking them down for web versions. If you have done this, then you can potentially make it work.
The ideal scenario is that your panelling is done on different layers with the art underneath. This way, you can potentially make pages with nice page-friendly panel layouts and copy-paste the art into them. Some panels might be cropped a little differently, but hopefully it'd work decently enough? You'll not get the flow of a comic where the page layouts and contents were designed for print, but in the same way, my pages are very much designed for print, so I can't easily do some cool flow techniques I could use if I made my pages for web first.