Why is the resolution of a scanned PDF Source Document not clear in Vault Viewer?
This is expected behavior for scanned PDF documents.
The image may appear skewed and unclear in the Vault Viewer. The PDF Source Document and Viewable Rendition may not have this issue in Adobe Acrobat because of Acrobat's features that enhance thin lines and smooth line art preferences.
The Vault document Viewer attempts to resolve this, but there are still some instances where it cannot correct it. This is due to Acrobat's feature manipulation of the images in the PDF. The Vault Viewer does not perform all of these optimizations and shows more of what the actual PDF file looks like.
Vault Rendition Documentation: PDF/A Viewable Renditions