There's a black box around the images when I print
A black box that appears to be behind the images when printing a PDF file is usually due to printing the file from a preview, or browser window, rather than printing directly from the file using a PDF viewer. This can also happen when using an older version of PDF viewing software, or when printer drivers are not updated.
If you are experiencing this with PDF files you have created, I would recommend downloading the latest version of Adobe Acrobat and printing directly from within Acrobat (open the file in Acrobat and then print). I would also recommend updating your printer drivers!
You might also like to try using the "Print as image" option in the print dialogue box, you'll find that option by clicking the "Advanced" tab after selecting print. Flattening the illustrations with the background before inserting them into the document can also help get around this issue.