Forms, Merging and Watermarks

Fillable Forms (AcroForm)

import com.itextpdf.forms.PdfAcroForm;
import com.itextpdf.forms.fields.PdfTextFormField;

PdfAcroForm form = PdfAcroForm.getAcroForm(pdf, true);
PdfTextFormField name = new PdfTextFormFieldBuilder(pdf, "name").createText();
name.setValue("Priya");
form.addField(name);

Merging PDFs

import com.itextpdf.kernel.utils.PdfMerger;

PdfDocument merged = new PdfDocument(new PdfWriter("out.pdf"));
PdfMerger merger = new PdfMerger(merged);
merger.merge(new PdfDocument(new PdfReader("a.pdf")), 1, 5);
merger.merge(new PdfDocument(new PdfReader("b.pdf")), 1, 2);
merged.close();

Watermarks are just semi-transparent text drawn under content with PdfCanvas + PdfExtGState.setFillOpacity(0.2f).