Is there a simple way I can achieve this? I seem to be struggling to get a straight answer on this from searching on Google and other forums.
Or is the only option to open my InDesign file and individually convert all my swatches and images to RGB? This would be a real pain for larger documents.
I would do it in Photoshop but I could do with leaving all the text intact and it will be a PDF that people can view online.
gs -sDEVICE=pdfwrite -dBATCH -dNOPAUSE -dCompatibilityLevel=1.4 -dColorConversionStrategy=/sRGB -dProcessColorModel=/DeviceRGB -dUseCIEColor=true -sOutputFile=output.pdf input.ps
The above was taken from this answer: How to convert PDF from CMYK to RGB, for displaying on iPad?
I dont have Ghosscript installed on my box yet but you could always try the reversal from this:
gswin32c.exe ^ -o c:/path/to/output-cmyk.pdf ^ -sDEVICE=pdfwrite ^ -dUseCIEColor ^ -sProcessColorModel=DeviceCMYK ^ -sColorConversionStrategy=CMYK ^ -sColorConversionStrategyForImages=CMYK ^ input-rgb.pdf
taken from this question: Script (or some other means) to convert RGB to CMYK in PDF?