I am converting multiple jpg images to a single PDF using following command
convert *.jpg mybook.pdf
but the pdf quality is not good.
Is there a way to retain the original quality of images in the pdf?
You might want to try using software like Adobe Acrobat, but there is no way to create quality in an image. Consider uploading to Google Docs, and then re-download the images as a PDF (if you don’t already have Adobe Acrobat).
Let's suppose your original images are with a definition of 300 dpi. You can use
It's possible to choose the density, the geometry of the page and so on...