There is another library called Pdfbox if you are unable to use iText.
https://pdfbox.apache.org/
With iText it is possible to merge (combine), then even with
new images, could be added as it appears.
The necessary you already have, the path, if static, can use directly or dynamically if you need to choose.
http://developers.itextpdf.com/
Ex:
private void combinaImagensEmPdf(String caminhoImagens, String caminhoSaida) {
try {
Document document = new Document();
PdfWriter.getInstance(document, new FileOutputStream("arquivo.pdf"));
document.open();
File files[] = new File(caminhoImagens).listFiles();
PdfPTable table = new PdfPTable(1);
for (File file : files) {
table.setWidthPercentage(100); //Altera e configura
table.addCell(criarCelulaDeImagem(file.getAbsolutePath()));
}
document.add(table);
document.close();
} catch (FileNotFoundException e) {
e.printStackTrace();
}
}
public static PdfPCell criarCelulaDeImagem(String caminhoImagens) {
Image img = Image.getInstance(caminhoImagens);
return new PdfPCell(img, true);
}
Ref: https://stackoverflow.com/questions/27425738/merge-multiple-images-in-a-pdf-file