How do I make the solder paste layer visible on the pads? I've seen it before but not sure what settings I should use now. I've tried changing the layer order and flipping the board but still not visible. It appears in my gerber viewer. It would be useful to be able to see the solder resist (negative) layer in EasyPC too.
You need to specify TopSolderPaste/BottomSolderPaste as a paste mask layer in Settings=>Design Tech=>Layers.
Also check the Paste mask layer settings Settings=>Design Tech=>Layer Types, as you can specify paste mask on thru hole pads, pads and vias (if you fancy) and you may wish to specify a slightly smaller paste size (minus) to the pad depending on the specification of the S/mount components you use.
Expanding on edrees' reply, if you're using the plot outputs based on the copper layers, such as 'Top Copper (paste), then the plots are being auto-generated from the copper layers so they won't be separately visible. There's a FAQ on adding custom layers on the website at this address: https://www.numberone.com/faq.asp?14
If you're doing this as part of a footprint, beware. Each layer uses a layer type. The layer type used for the custom layers MUST match between the footprint and the design or the layer information won't load correctly.
Sometimes the easiest way to ensure this is to edit an existing technology file , adding the new layers to create your own custom one that can then be used both for footprints and pcb designs, ensuring a match.