I've used PDF 文件夹 with good success. Here's a sample of what the code looks like (back from version 0.7.2), that likely came from one of the provided examples:
// load the document
System.out.println("Reading document: " + filename);
PDDocument doc = null;
doc = PDDocument.load(filename);
// look at all the document information
PDDocumentInformation info = doc.getDocumentInformation();
COSDictionary dict = info.getDictionary();
List l = dict.keyList();
for (Object o : l) {
//System.out.println(o.toString() + " " + dict.getString(o));
System.out.println(o.toString());
}
// look at the document catalog
PDDocumentCatalog cat = doc.getDocumentCatalog();
System.out.println("Catalog:" + cat);
List<PDPage> lp = cat.getAllPages();
System.out.println("# Pages: " + lp.size());
PDPage page = lp.get(4);
System.out.println("Page: " + page);
System.out.println("\tCropBox: " + page.getCropBox());
System.out.println("\tMediaBox: " + page.getMediaBox());
System.out.println("\tResources: " + page.getResources());
System.out.println("\tRotation: " + page.getRotation());
System.out.println("\tArtBox: " + page.getArtBox());
System.out.println("\tBleedBox: " + page.getBleedBox());
System.out.println("\tContents: " + page.getContents());
System.out.println("\tTrimBox: " + page.getTrimBox());
List<PDAnnotation> la = page.getAnnotations();
System.out.println("\t# Annotations: " + la.size());