Reanalyzing data - improve existing graphs and data visualization

I am looking for a tool that I can use to change graphs or tables from published scientific papers and improve them.
For instance, I would like to receive ideas on how to show the data from a table (pdf or png format) graphically.
For an existing graph (pdf or png format), I would like to receive ideas in how to improve it.
I would also like to receive creative but still scientific ideas to represent select pieces of information.