Get the number of children attached to a layer display order node.
int pdfGetLayerOrderNumChildren(PDFHandle pdf, PDFLayerOrderHandle order)
PDF files with layers contain a tree structure that specifies the way layers are intended to be displayed to the user. Each node in the tree has either a name or a layer. Named nodes are used to provide a hierarchical structure for the layers, with labels to help the user. Each node also optionally has a list of child nodes.

This function returns the number of children that the specified layer order tree node has.

scanLayerOrder(pdfGetLayerOrderRoot(pdf)); ... void scanLayerOrder(PDFLayerOrderHandle order) { char *name; int length; PDFLayerHandle layer; int nChildren, i; if (pdfGetLayerOrderIsName(pdf, order)) { /* this node has a name */ name = pdfGetLayerOrderName(pdf, order, &length); ... pdfFreeMemory(name); } else { /* this node has a layer */ layer = pdfGetLayerOrderLayer(pdf, order); ... } nChildren = pdfGetLayerOrderNumChildren(pdf, order); for (i = 0; i < nChildren; ++i) { scanLayerOrder(pdfGetLayerOrderChild(pdf, order, i); } }