The Walmart PDF (10793-sample3.pdf) has a secondary issue related to soft-masks and gradient paint. The soft mask issue can be compensated for by looking for the presence of a soft-mask in the graphics state. If not present then we can fall back to the regular transparency values specified by ca and CA. This doesn't match up perfectly with the spec but provides a slight better rendering as a compromise.
There is a very subtle gradient painted on the pages 6 -> 13, the gradient uses a type 1 function which isn't currently supported in ICEpdf. In this particular case the type 1 shadding function is actually represented by a straight line and technically would follow the same implementation of a Type 2 axial shading. Some more work would be needed for us to support type 1 shadding, however this is the only example that I have ever encountered.