Pdf wrong thumbnails

Hello, I have online a repository (https://aol-apothetirio.com) and the files are PDF’s . The thumbnails are too small. I tried jpg and it seems allright but we need to have pdf because of the pages.
Any idea fixing that ?
Thanks

Those PDFs use a cropping feature that we’re currently not paying attention to when making thumbnails.

The resulting thumbnails aren’t actually smaller, they just contain a white “page” around your actual desired image. There’s a feature of ImageMagick, the software we use to make thumbnails, that can handle these kinds of PDFs and avoid this problem, but we’ll have to make some code changes in Omeka to use that feature, so it will take at least a little while for that fix to come out.

You may be able to alter your PDFs in the meantime to crop in a different way that doesn’t cause this issue, or you could upload both the PDF and an image copy, with the image used just for the thumbnail.