Large MultiPage PDF generated using Aspose PDF 7.2

I have been using Aspose 7.2 PDF for .Net 4 framework. I have a bunch of images (approx 55 pages) which i will be converting to PDF format. When it gets converted to MultiPage PDF, its file size becomes significantly Large. 

For example : For sample attached image, when the same image used to create 55 MultiPage PDF, it would create larger Multipage PDF.

Please let us know how can we achieve optimum quality along with Minimum size.