Redlining is supported via transforming to PDF format. If you want to redline a plot file in SPLOT, you must first convert it to PDF and open the PDF file in the integrated PDF viewer. This PDF viewer has a powerful markup capability with rich set of tools. Using the e-mail function directly in PDF viewer you can also dispatch the PDF file after editing.
The whole redlining process can be quickly started and performed with the corresponding toolbar button either for the current file only ( button in the main toolbar) or as batch process for any selected plot file(s) in the embedded explorer ( button in the explorer).