Technology preview of PDF Layers support was released with APP V11 M030 for frames with plans to extend this to blocks in the near future. PDF watermarks and Alt text are now possible, cool!
This JS sample code creates a PDF layer and a frame which the layer property is assigned to.

var layer;
layerDef = template.content.getPDFLayer(“logoLayer”);
if (!layerDef) layerDef = template.content.createPDFLayer(“logoLayer”);

layerDef.pageElement = fPDFLayer.LAYER_LOGO;
layerDef.viewState = true;
layerDef.printState = true;
layerDef.onPanel = true;
layerDef.exportState = true;
layerDef.visibleState = true;

var frameDef;
frameDef = template.content.getFrame(“logoFrame”);
if (!frameDef) frameDef = template.content.createFrame(“logoFrame”);

frameDef.x = “70mm”;
frameDef.y = “230mm”;
frameDef.height = “30mm”;
frameDef.width = “100mm”;
//frameDef.backgroundColor = “blue”;
frameDef.raster=”TFLogoOr1″;
frameDef.rasterScaleX=fFrame.SCALE_FIT;
frameDef.rasterScaleY=fFrame.SCALE_PRESERVE;
frameDef.avoid=0;
frameDef.number=0;
frameDef.pdfLayer = layerDef;

if (!template.content.pages[0].mainLayer.frames.logoFrame) template.content.pages[0].mainLayer.addFrame(frameDef);