diff --git a/frontend/src/preview/PdfViewer.tsx b/frontend/src/preview/PdfViewer.tsx
index 14ab38f..f8bf92b 100644
--- a/frontend/src/preview/PdfViewer.tsx
+++ b/frontend/src/preview/PdfViewer.tsx
@@ -10,6 +10,7 @@ import React, {
 import type { CSSProperties, JSX, MutableRefObject, RefObject } from 'react';
 import {
   GlobalWorkerOptions,
+  PasswordResponses,
   getDocument,
 } from 'pdfjs-dist';
 import type {
@@ -106,6 +107,10 @@ const PdfViewer = ({ src, title, className, viewportRef }: PdfViewerProps): JSX.
     velocity: 0,
   });
   const scrollElementRef = useRef<HTMLElement | null>(null);
+  const [isEncrypted, setIsEncrypted] = useState(false);
+  const [passwordError, setPasswordError] = useState(false);
+  const [passwordCallback, setPasswordCallback] = useState<((password: string) => void) | null>(null);
+  const passwordInputRef = useRef<HTMLInputElement>(null);
 
   const requestQueueFlush = useCallback(() => {
     const queue = renderQueueRef.current;
@@ -283,6 +288,14 @@ const PdfViewer = ({ src, title, className, viewportRef }: PdfViewerProps): JSX.
           url: src,
           wasmUrl,
         });
+        loadingTask.onPassword = (callback, reason) => {
+          setIsEncrypted(true);
+          setPasswordCallback(() => callback);
+          if (reason === PasswordResponses.INCORRECT_PASSWORD) {
+            setPasswordError(true);
+          }
+        };
+
         const pdf = await loadingTask.promise;
         if (cancelled) {
           await pdf.destroy();
@@ -342,6 +355,13 @@ const PdfViewer = ({ src, title, className, viewportRef }: PdfViewerProps): JSX.
     };
   }, [ensureWasmUrl, renderWidth, src]);
 
+  const handlePasswordSubmit = useCallback((event: React.FormEvent) => {
+    event.preventDefault();
+    if (passwordCallback && passwordInputRef.current) {
+      passwordCallback(passwordInputRef.current.value);
+    }
+  }, [passwordCallback]);
+
   const viewerClasses = ['document-viewer__object', 'document-viewer__object--pdf', className]
     .filter(Boolean)
     .join(' ');
@@ -553,22 +573,55 @@ const PdfViewer = ({ src, title, className, viewportRef }: PdfViewerProps): JSX.
 
   return (
     <div className={viewerClasses}>
-      <div
-        ref={containerRef}
-        className={`pdf-viewer__canvas-stack pdf-viewer__canvas-stack--${viewMode}`}
-        role="document"
-        aria-label={title || 'PDF document'}
-        style={stackStyle}
-      >
-        {pageElements}
-      </div>
-      {showStatus ? (
-        <div className={statusClasses}>
-          <div className="document-viewer__message">
-            {statusMessage}
-          </div>
+      {isEncrypted && !pdfRef.current ? (
+        <div
+          className="pdf-viewer__password-container"
+          onClick={(e) => e.stopPropagation()}
+          onKeyDown={(e) => e.stopPropagation()}
+        >
+          <form onSubmit={handlePasswordSubmit} className="pdf-viewer__password-form">
+            <div className="pdf-viewer__password-message">
+              This document is password protected.
+            </div>
+            <div className="pdf-viewer__password-input-group">
+              <input
+                ref={passwordInputRef}
+                type="password"
+                className="pdf-viewer__password-input"
+                placeholder="Enter password"
+                autoFocus
+              />
+              <button type="submit" className="button button--primary">
+                Unlock
+              </button>
+            </div>
+            {passwordError ? (
+              <div className="pdf-viewer__password-error">
+                Incorrect password. Please try again.
+              </div>
+            ) : null}
+          </form>
         </div>
-      ) : null}
+      ) : (
+        <>
+          <div
+            ref={containerRef}
+            className={`pdf-viewer__canvas-stack pdf-viewer__canvas-stack--${viewMode}`}
+            role="document"
+            aria-label={title || 'PDF document'}
+            style={stackStyle}
+          >
+            {pageElements}
+          </div>
+          {showStatus ? (
+            <div className={statusClasses}>
+              <div className="document-viewer__message">
+                {statusMessage}
+              </div>
+            </div>
+          ) : null}
+        </>
+      )}
     </div>
   );
 };
diff --git a/frontend/src/styles/documents/viewer.css b/frontend/src/styles/documents/viewer.css
index 8985453..3d0e6f6 100644
--- a/frontend/src/styles/documents/viewer.css
+++ b/frontend/src/styles/documents/viewer.css
@@ -22,8 +22,8 @@
   min-height: auto;
 }
 
-.document-viewer-panel__body > .document-viewer,
-.document-viewer-panel__body > .document-viewer--loading {
+.document-viewer-panel__body>.document-viewer,
+.document-viewer-panel__body>.document-viewer--loading {
   flex: 1;
 }
 
@@ -182,6 +182,7 @@
   flex: 1;
   grid-area: details;
 }
+
 .document-viewer__tabs-wrapper {
   display: flex;
   flex-direction: column;
@@ -564,11 +565,69 @@
   width: 1rem;
   height: 1rem;
 }
+
 .document-viewer__summary-tab-content {
   padding-top: 0.5rem;
 }
+
 .pdf-viewer__page-wrapper--contain .pdf-viewer__page {
   width: auto;
   max-width: 100vw;
   max-height: 100vh;
 }
+
+.pdf-viewer__password-container {
+  display: flex;
+  flex-direction: column;
+  align-items: center;
+  justify-content: center;
+  height: 100%;
+  width: 100%;
+  background: var(--surface-subtle);
+}
+
+.pdf-viewer__password-form {
+  display: flex;
+  flex-direction: column;
+  align-items: center;
+  gap: 1rem;
+  padding: 2rem;
+  background: var(--surface);
+  box-shadow: var(--shadow-pop);
+  max-width: 400px;
+  margin: 1rem;
+  box-sizing: border-box;
+}
+
+.pdf-viewer__password-message {
+  font-size: 1rem;
+  font-weight: 500;
+  color: var(--fg);
+  text-align: center;
+}
+
+.pdf-viewer__password-input-group {
+  display: flex;
+  gap: 0.5rem;
+  width: 100%;
+  box-sizing: border-box;
+}
+
+.pdf-viewer__password-input-group .button {
+  flex-shrink: 0;
+}
+
+.pdf-viewer__password-input {
+  flex: 1;
+  min-width: 0;
+  padding: 0.5rem;
+  border: 1px solid var(--outline);
+  border-radius: 0.25rem;
+  font-size: 1rem;
+  box-sizing: border-box;
+}
+
+.pdf-viewer__password-error {
+  color: var(--danger);
+  font-size: 0.9rem;
+}
\ No newline at end of file