Check the -resample option of ImageMagick. You can specify 300x300 pixel grid and that has worked well for creating high res.
No it doesn't have to be a hell of a job. Once you get the parameters right it can extract ALL of the pages from a PDF automatically in whatever format, resolution, pixel density, etc. that you desire.
Worth learning ImageMagick when you are processing large amounts of image.
Also whatever your platform is, you may have to learn how the PDF parameters are set, the parameters that determine how your PDF creator software actually turns embedded images to PDF. Usually this is hidden from the user. Some O/S's expose it but in most it is deeply buried. Worth the research & learning.