Fuentes en las celdas

PdfPCell cellMision = new PdfPCell(new Paragraph(pv.getMision(), FontFactory.getFont("arial", 9, Font.NORMAL)));

Definimos el tamaño de fuente mas pequeño para mision.

Método

 public void imprimir() {

//        com.lowagie.text.Document document = new com.lowagie.text.Document(PageSize.LETTER);
        com.lowagie.text.Document document = new com.lowagie.text.Document(PageSize.A4.rotate());
        
              
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        try {
            PdfWriter.getInstance(document, baos);
            //METADATA

            document.open();

            document.add(new Paragraph(" PROGRAMACION DE FLOTA VEHICULAR \n"));

            DateFormat formatter = new SimpleDateFormat("dd/MM/yy '-' hh:mm:ss:");
            Date currentDate = new Date();
            String date = formatter.format(currentDate);
            document.add(new Paragraph("Fecha Generado: " + date));
            document.add(new Paragraph("\n"));

            PdfPTable table = new PdfPTable(7);

//                  table.setTotalWidth(new float[]{ 20,72, 110, 95, 170, 72 });
            table.setTotalWidth(new float[]{20, 100,85,85,225, 72, 110});
            table.setLockedWidth(true);

            PdfPCell cell = new PdfPCell(new Paragraph("id",
                    FontFactory.getFont("arial", // fuente
                            12, // tamaño
                            Font.BOLD)));
            cell.setHorizontalAlignment(Element.ALIGN_CENTER);

            cell.setColspan(1);
            table.addCell(cell);

          //  cell = new PdfPCell(new Paragraph("ID", FontFactory.getFont("arial", 8, Font.BOLD)));

            table.addCell("fechapartida");
            table.addCell("dia");
            table.addCell("unidad");
            table.addCell("mision");
            
            table.addCell("conductor");

            table.addCell("placa");

            for (ProgramacionVehicular pv : programacionVehicular) {
                String date1 = formatter.format(pv.getFechahorasalida());

                table.addCell(pv.getIdviaje().toString());
                table.addCell(date1);
                table.addCell(pv.getNombredia());
                table.addCell(pv.getUnidad());
               PdfPCell cellMision = new PdfPCell(new Paragraph(pv.getMision(), FontFactory.getFont("arial", 9, Font.NORMAL)));
                table.addCell(cellMision );
//                table.addCell(pv.getMision());
                table.addCell(pv.getConductor());
                table.addCell(pv.getPlaca());

            }
            document.add(table);
        } catch (Exception ex) {
            System.out.println("Error " + ex.getMessage());
        }
        document.close();
        FacesContext context = FacesContext.getCurrentInstance();
        Object response = context.getExternalContext().getResponse();
        if (response instanceof HttpServletResponse) {
            HttpServletResponse hsr = (HttpServletResponse) response;
            hsr.setContentType("application/pdf");
            hsr.setHeader("Contentdisposition", "attachment;filename=report.pdf");
            //        hsr.setHeader("Content-disposition", "attachment");
            hsr.setContentLength(baos.size());
            try {
                ServletOutputStream out = hsr.getOutputStream();
                baos.writeTo(out);
                out.flush();
            } catch (IOException ex) {
                System.out.println("Error:  " + ex.getMessage());
            }
            context.responseComplete();
        }
    }