diff --git a/src/components/InvoiceModal.js b/src/components/InvoiceModal.js
index a28f140..9e11116 100644
--- a/src/components/InvoiceModal.js
+++ b/src/components/InvoiceModal.js
@@ -1,4 +1,4 @@
-import { getInvoiceById, updateInvoice, validateInvoice, addInvoiceLine, deleteInvoiceLine, addPayment, getPayments } from '../services/invoices.js';
+import { getInvoiceById, updateInvoice, validateInvoice, addInvoiceLine, deleteInvoiceLine, addPayment, getPayments, downloadInvoicePdf } from '../services/invoices.js';
 import { showConfirmExitModal, FormChangeTracker } from './ConfirmExitModal.js';
 
 export function InvoiceModal(invoiceId, onClose, onUpdate) {
@@ -79,6 +79,7 @@ export function InvoiceModal(invoiceId, onClose, onUpdate) {
 
     const isDraft = invoice.status === 'draft';
     const canEdit = isDraft || invoice.status === 'validated' || invoice.status === 'unpaid';
+    const canDownloadPdf = invoice.status === 'validated' || invoice.status === 'paid';
 
     modalContent.innerHTML = `
       <div class="modal-header">
@@ -317,6 +318,7 @@ export function InvoiceModal(invoiceId, onClose, onUpdate) {
 
       <div class="modal-footer">
         <div class="footer-actions-left">
+          ${canDownloadPdf ? '<button type="button" class="btn-download-invoice btn-primary"><svg width="16" height="16" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="1.5" stroke-linecap="round" stroke-linejoin="round" style="vertical-align: middle; margin-right: 4px;"><path d="M21 15v4a2 2 0 0 1-2 2H5a2 2 0 0 1-2-2v-4"/><polyline points="7 10 12 15 17 10"/><line x1="12" y1="15" x2="12" y2="3"/></svg>Descargar factura</button>' : ''}
           ${isDraft ? '<button type="button" class="btn-validate btn-success"><svg width="16" height="16" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="1.5" stroke-linecap="round" stroke-linejoin="round" style="vertical-align: middle; margin-right: 4px;"><polyline points="20 6 9 17 4 12"/></svg>Validar Factura</button>' : ''}
         </div>
         <div class="footer-actions-right">
@@ -356,6 +358,10 @@ export function InvoiceModal(invoiceId, onClose, onUpdate) {
     const validateBtn = modal.querySelector('.btn-validate');
     validateBtn?.addEventListener('click', handleValidate);
 
+    // Botón descargar factura PDF
+    const downloadBtn = modal.querySelector('.btn-download-invoice');
+    downloadBtn?.addEventListener('click', handleDownloadPdf);
+
     // Botón añadir línea
     const addLineBtn = modal.querySelector('.btn-add-line');
     addLineBtn?.addEventListener('click', toggleAddLineForm);
@@ -510,6 +516,42 @@ export function InvoiceModal(invoiceId, onClose, onUpdate) {
     }
   };
 
+  // Manejar descarga del PDF
+  const handleDownloadPdf = async () => {
+    if (!invoice?.number) {
+      alert('No se puede descargar la factura porque no tiene número.');
+      return;
+    }
+
+    const downloadBtn = modal.querySelector('.btn-download-invoice');
+    const originalHtml = downloadBtn?.innerHTML;
+
+    try {
+      if (downloadBtn) {
+        downloadBtn.disabled = true;
+        downloadBtn.textContent = 'Descargando...';
+      }
+
+      const pdfBlob = await downloadInvoicePdf(invoice.number);
+      const blobUrl = URL.createObjectURL(pdfBlob);
+      const link = document.createElement('a');
+      link.href = blobUrl;
+      link.download = `Factura-${invoice.number}.pdf`;
+      document.body.appendChild(link);
+      link.click();
+      link.remove();
+      URL.revokeObjectURL(blobUrl);
+    } catch (error) {
+      console.error('Error al descargar factura:', error);
+      alert('Error al descargar la factura: ' + error.message);
+    } finally {
+      if (downloadBtn) {
+        downloadBtn.disabled = false;
+        downloadBtn.innerHTML = originalHtml;
+      }
+    }
+  };
+
   // Mostrar/ocultar formulario de añadir línea
   const toggleAddLineForm = () => {
     const form = modal.querySelector('.add-line-form');
diff --git a/src/services/invoices.js b/src/services/invoices.js
index 11c8f6f..69b7644 100644
--- a/src/services/invoices.js
+++ b/src/services/invoices.js
@@ -123,6 +123,24 @@ export async function getPayments(invoiceId) {
     return await response.json();
 }
 
+export async function downloadInvoicePdf(invoiceNumber) {
+    const token = localStorage.getItem('token');
+    const response = await fetch(`${API_BASE_URL}/api/document/invoice/${encodeURIComponent(invoiceNumber)}/pdf`, {
+        method: 'GET',
+        headers: {
+            'Authorization': `Bearer ${token}`,
+            'Accept': 'application/pdf'
+        }
+    });
+
+    if (!response.ok) {
+        const error = await response.json().catch(() => ({}));
+        throw new Error(error.detail || 'Error al descargar la factura');
+    }
+
+    return await response.blob();
+}
+
 export async function deleteInvoice(id) {
     // Nota: No hay endpoint DELETE en el OpenAPI spec, 
     // pero podríamos usar el endpoint de cambio de estado a "canceled"