Build Web app/server side GUI to input text and build custom looking pdf and html pages

I want to build a GUI php/html or whatever you think is best to build in for creating a webpage/webapp hosted on my website that will allow me to input rows of marked rft styled text that I can cut and paste into the web app. the web app will then render the text as pdf and an html5 webpage that I can use as an iframe or as freestanding on my website. The formate for the GUI will be text boxes and then a preview as pdf and preview as html button. Then an export as html and pdf button. The text boxes will be 3 columns of equal size. and then unlimited amounts of rows within those columns. The rows should be equal height across the 3 columns defaulting with whatever row has the most text in it as being the boundries for that particular row across all three columns. This is esssentially like a table output style, but I prefer to have something that doesn't use tables because I want it to auto resize/format well for all screen sizes.