It looks like the generated pdf was damaged.
1 0 obj
/Title (R Graphics Output)
/Producer (R 3.0.3)
2 0 obj
<< /Type /Catalog /Pages 3 0 R >>
7 0 obj
<< /Type /Page /Parent 3 0 R /Contents 8 0 R /Resources 4 0 R >>
I made a new graph and was successfully able to view the newly generated Rplots.pdf inside codio with the preview button Current File (static).
Very happy now