diff --git a/apps/red-ui/src/app/modules/account/screens/user-profile/user-profile-screen/user-profile-screen.component.html b/apps/red-ui/src/app/modules/account/screens/user-profile/user-profile-screen/user-profile-screen.component.html
index 5291221dd..4d6c2172c 100644
--- a/apps/red-ui/src/app/modules/account/screens/user-profile/user-profile-screen/user-profile-screen.component.html
+++ b/apps/red-ui/src/app/modules/account/screens/user-profile/user-profile-screen/user-profile-screen.component.html
@@ -28,11 +28,21 @@
             <div class="iqser-input-group">
                 <a [href]="changePasswordUrl" target="_blank"> {{ 'user-profile-screen.actions.change-password' | translate }}</a>
             </div>
+            <div class="iqser-input-group">
+                <mat-slide-toggle color="primary" formControlName="darkTheme">
+                    {{ 'user-profile-screen.form.dark-theme' | translate }}
+                </mat-slide-toggle>
+            </div>
         </div>
     </div>
 
     <div class="dialog-actions">
-        <button [disabled]="form.invalid || !(profileChanged || languageChanged)" color="primary" mat-flat-button type="submit">
+        <button
+            [disabled]="form.invalid || !(profileChanged || languageChanged || themeChanged)"
+            color="primary"
+            mat-flat-button
+            type="submit"
+        >
             {{ 'user-profile-screen.actions.save' | translate }}
         </button>
     </div>
diff --git a/apps/red-ui/src/app/modules/account/screens/user-profile/user-profile-screen/user-profile-screen.component.ts b/apps/red-ui/src/app/modules/account/screens/user-profile/user-profile-screen/user-profile-screen.component.ts
index e835758e3..941c9ff75 100644
--- a/apps/red-ui/src/app/modules/account/screens/user-profile/user-profile-screen/user-profile-screen.component.ts
+++ b/apps/red-ui/src/app/modules/account/screens/user-profile/user-profile-screen/user-profile-screen.component.ts
@@ -10,7 +10,7 @@ import { UserService } from '@services/user.service';
 import { ConfigService } from '@services/config.service';
 import { LanguageService } from '../../../../../i18n/language.service';
 import { firstValueFrom } from 'rxjs';
-import { UserPreferenceService } from '../../../../../services/user-preference.service';
+import { UserPreferenceService } from '@services/user-preference.service';
 
 @Component({
     selector: 'redaction-user-profile-screen',
@@ -34,6 +34,7 @@ export class UserProfileScreenComponent extends BaseFormComponent implements OnI
         private readonly _formBuilder: UntypedFormBuilder,
         private readonly _languageService: LanguageService,
         protected readonly _translateService: TranslateService,
+        protected readonly _userPreferenceService: UserPreferenceService,
     ) {
         super();
         this._loadingService.start();
@@ -44,9 +45,14 @@ export class UserProfileScreenComponent extends BaseFormComponent implements OnI
         return this.#profileModel['language'] !== this.form.get('language').value;
     }
 
+    get themeChanged(): boolean {
+        return this._profileModel['darkTheme'] !== this.form.get('darkTheme').value;
+    }
+
     get profileChanged(): boolean {
         const keys = Object.keys(this.form.getRawValue());
         keys.splice(keys.indexOf('language'), 1);
+        keys.splice(keys.indexOf('darkTheme'), 1);
 
         for (const key of keys) {
             if (this.#profileModel[key] !== this.form.get(key).value) {
@@ -86,6 +92,10 @@ export class UserProfileScreenComponent extends BaseFormComponent implements OnI
             await firstValueFrom(this._userService.loadAll());
         }
 
+        if (this.themeChanged) {
+            await this._userPreferenceService.saveTheme(this.form.get('darkTheme').value ? 'dark' : 'light');
+        }
+
         this._initializeForm();
     }
 
@@ -95,6 +105,7 @@ export class UserProfileScreenComponent extends BaseFormComponent implements OnI
             firstName: [undefined],
             lastName: [undefined],
             language: [undefined],
+            darkTheme: [false],
         });
     }
 
@@ -106,6 +117,7 @@ export class UserProfileScreenComponent extends BaseFormComponent implements OnI
                 firstName: this._userService.currentUser.firstName,
                 lastName: this._userService.currentUser.lastName,
                 language: this._languageService.currentLanguage,
+                darkTheme: this._userPreferenceService.getTheme() === 'dark',
             };
             if (this._userService.currentUser.email) {
                 // disable email if it's already set
diff --git a/apps/red-ui/src/app/modules/admin/screens/watermark/watermark-screen/watermark-screen.component.scss b/apps/red-ui/src/app/modules/admin/screens/watermark/watermark-screen/watermark-screen.component.scss
index bbdca01c2..18550f5ed 100644
--- a/apps/red-ui/src/app/modules/admin/screens/watermark/watermark-screen/watermark-screen.component.scss
+++ b/apps/red-ui/src/app/modules/admin/screens/watermark/watermark-screen/watermark-screen.component.scss
@@ -39,7 +39,7 @@
             width: 60px;
             height: 60px;
             border-radius: 8px;
-            background-color: var(--iqser-grey-6);
+            background-color: var(--iqser-btn-bg);
             color: var(--iqser-grey-7);
             align-items: center;
             justify-content: center;
@@ -53,7 +53,7 @@
             }
 
             &:not(.disabled):not(.active):hover {
-                background-color: darken(variables.$grey-6, 2);
+                background-color: var(--iqser-btn-bg-hover);
             }
 
             &:not(:last-child) {
diff --git a/apps/red-ui/src/app/modules/admin/screens/watermark/watermark-screen/watermark-screen.component.ts b/apps/red-ui/src/app/modules/admin/screens/watermark/watermark-screen/watermark-screen.component.ts
index a1facac72..61fd8a519 100644
--- a/apps/red-ui/src/app/modules/admin/screens/watermark/watermark-screen/watermark-screen.component.ts
+++ b/apps/red-ui/src/app/modules/admin/screens/watermark/watermark-screen/watermark-screen.component.ts
@@ -12,7 +12,8 @@ import { WatermarkService } from '@services/entity-services/watermark.service';
 import { firstValueFrom, Observable, of, switchMap } from 'rxjs';
 import { catchError, tap } from 'rxjs/operators';
 import { ActivatedRoute } from '@angular/router';
-import { LicenseService } from '../../../../../services/license.service';
+import { LicenseService } from '@services/license.service';
+import { UserPreferenceService } from '@services/user-preference.service';
 
 export const DEFAULT_WATERMARK: IWatermark = {
     text: null,
@@ -48,6 +49,7 @@ export class WatermarkScreenComponent implements OnInit {
         @Inject(BASE_HREF_FN) private readonly _convertPath: BaseHrefFn,
         private readonly _watermarkService: WatermarkService,
         private readonly _changeDetectorRef: ChangeDetectorRef,
+        private readonly _userPreferenceService: UserPreferenceService,
     ) {
         this._loadingService.start();
         this.#dossierTemplateId = route.snapshot.paramMap.get(DOSSIER_TEMPLATE_ID);
@@ -137,6 +139,8 @@ export class WatermarkScreenComponent implements OnInit {
             ).then(instance => {
                 this._instance = instance;
 
+                instance.UI.setTheme(this._userPreferenceService.getTheme());
+
                 instance.Core.documentViewer.on('documentLoaded', async () => {
                     this._loadingService.stop();
                     await this._drawWatermark();
diff --git a/apps/red-ui/src/app/modules/pdf-viewer/services/pdf-viewer.service.ts b/apps/red-ui/src/app/modules/pdf-viewer/services/pdf-viewer.service.ts
index b35624d90..6adad4f0a 100644
--- a/apps/red-ui/src/app/modules/pdf-viewer/services/pdf-viewer.service.ts
+++ b/apps/red-ui/src/app/modules/pdf-viewer/services/pdf-viewer.service.ts
@@ -13,6 +13,7 @@ import { Rgb } from '../utils/types';
 import { asList } from '../utils/functions';
 import { TranslateService } from '@ngx-translate/core';
 import { LicenseService } from '@services/license.service';
+import { UserPreferenceService } from '@services/user-preference.service';
 import TextTool = Core.Tools.TextTool;
 import Annotation = Core.Annotations.Annotation;
 import TextHighlightAnnotation = Core.Annotations.TextHighlightAnnotation;
@@ -53,6 +54,7 @@ export class PdfViewer {
         private readonly _activatedRoute: ActivatedRoute,
         private readonly _licenseService: LicenseService,
         private readonly _translateService: TranslateService,
+        private readonly _userPreferenceService: UserPreferenceService,
         @Inject(BASE_HREF_FN) private readonly _convertPath: BaseHrefFn,
     ) {}
 
@@ -133,6 +135,7 @@ export class PdfViewer {
         this.#instance = await this.#getInstance(htmlElement);
 
         await this.PDFNet.initialize(this._licenseService.activeLicenseKey);
+        this.#instance.UI.setTheme(this._userPreferenceService.getTheme());
         this._logger.info('[PDF] Initialized');
 
         this.documentViewer = this.#instance.Core.documentViewer;
diff --git a/apps/red-ui/src/app/services/user-preference.service.ts b/apps/red-ui/src/app/services/user-preference.service.ts
index e12759a5d..d426b3349 100644
--- a/apps/red-ui/src/app/services/user-preference.service.ts
+++ b/apps/red-ui/src/app/services/user-preference.service.ts
@@ -48,11 +48,12 @@ export class UserPreferenceService extends GenericService<UserAttributes> {
     }
 
     getTheme(): string {
-        return this._getAttribute(KEYS.theme, 'dark');
+        return this._getAttribute(KEYS.theme, 'light');
     }
 
     async saveTheme(theme: 'light' | 'dark'): Promise<void> {
         await this._save(KEYS.theme, theme);
+        window.location.reload();
     }
 
     getLanguage(): string {
diff --git a/apps/red-ui/src/assets/i18n/de.json b/apps/red-ui/src/assets/i18n/de.json
index a71f6718d..86e26ec43 100644
--- a/apps/red-ui/src/assets/i18n/de.json
+++ b/apps/red-ui/src/assets/i18n/de.json
@@ -2058,6 +2058,7 @@
       "save": "Änderungen speichern"
     },
     "form": {
+      "dark-theme": "",
       "email": "Email",
       "first-name": "Vorname",
       "last-name": "Nachname"
diff --git a/apps/red-ui/src/assets/i18n/en.json b/apps/red-ui/src/assets/i18n/en.json
index 5eca70ac2..f67ea9c87 100644
--- a/apps/red-ui/src/assets/i18n/en.json
+++ b/apps/red-ui/src/assets/i18n/en.json
@@ -2058,6 +2058,7 @@
       "save": "Save Changes"
     },
     "form": {
+      "dark-theme": "Dark Theme",
       "email": "Email",
       "first-name": "First name",
       "last-name": "Last name"
diff --git a/libs/red-domain/src/lib/users/profile.ts b/libs/red-domain/src/lib/users/profile.ts
index d45a837bd..e53543392 100644
--- a/libs/red-domain/src/lib/users/profile.ts
+++ b/libs/red-domain/src/lib/users/profile.ts
@@ -4,4 +4,5 @@ export interface IProfile {
     firstName: string;
     lastName: string;
     language: string;
+    darkTheme: boolean;
 }