diff --git a/frontend/public/locales/en-GB/translation.toml b/frontend/public/locales/en-GB/translation.toml
index a69ed9cdf..3b7797f9e 100644
--- a/frontend/public/locales/en-GB/translation.toml
+++ b/frontend/public/locales/en-GB/translation.toml
@@ -2389,6 +2389,11 @@ note = "Flattening removes interactive elements from the PDF, making them non-ed
 label = "Flatten only forms"
 desc = "Only flatten form fields, leaving other interactive elements intact"
 
+[flatten.renderDpi]
+label = "Rendering DPI (optional, recommended 150 DPI)"
+help = "Leave blank to use the system default. Higher DPI sharpens output but increases processing time and file size."
+placeholder = "e.g. 150"
+
 [flatten.results]
 title = "Flatten Results"
 
diff --git a/frontend/src/core/components/tools/flatten/FlattenSettings.tsx b/frontend/src/core/components/tools/flatten/FlattenSettings.tsx
index ae8b1ecf5..b8e97f8ef 100644
--- a/frontend/src/core/components/tools/flatten/FlattenSettings.tsx
+++ b/frontend/src/core/components/tools/flatten/FlattenSettings.tsx
@@ -1,4 +1,4 @@
-import { Stack, Text, Checkbox } from "@mantine/core";
+import { Stack, Text, Checkbox, NumberInput } from "@mantine/core";
 import { useTranslation } from "react-i18next";
 import { FlattenParameters } from "@app/hooks/tools/flatten/useFlattenParameters";
 
@@ -28,6 +28,20 @@ const FlattenSettings = ({ parameters, onParameterChange, disabled = false }: Fl
           }
         />
       </Stack>
+
+      {!parameters.flattenOnlyForms && (
+        <NumberInput
+          label={t('flatten.renderDpi.label', 'Rendering DPI')}
+          description={t('flatten.renderDpi.help', 'Leave blank to use the system default. Higher DPI sharpens output but increases processing time and file size.')}
+          placeholder={t('flatten.renderDpi.placeholder', 'e.g. 150')}
+          value={parameters.renderDpi ?? undefined}
+          onChange={(value) => onParameterChange('renderDpi', value != null && value !== '' ? Number(value) : undefined)}
+          disabled={disabled}
+          min={72}
+          max={2400}
+          step={50}
+        />
+      )}
     </Stack>
   );
 };
diff --git a/frontend/src/core/hooks/tools/flatten/useFlattenOperation.ts b/frontend/src/core/hooks/tools/flatten/useFlattenOperation.ts
index f36b9d078..49b83a0bb 100644
--- a/frontend/src/core/hooks/tools/flatten/useFlattenOperation.ts
+++ b/frontend/src/core/hooks/tools/flatten/useFlattenOperation.ts
@@ -8,6 +8,9 @@ export const buildFlattenFormData = (parameters: FlattenParameters, file: File):
   const formData = new FormData();
   formData.append('fileInput', file);
   formData.append('flattenOnlyForms', parameters.flattenOnlyForms.toString());
+  if (parameters.renderDpi != null) {
+    formData.append('renderDpi', parameters.renderDpi.toString());
+  }
   return formData;
 };
 
diff --git a/frontend/src/core/hooks/tools/flatten/useFlattenParameters.ts b/frontend/src/core/hooks/tools/flatten/useFlattenParameters.ts
index af47ab3e1..3a383d674 100644
--- a/frontend/src/core/hooks/tools/flatten/useFlattenParameters.ts
+++ b/frontend/src/core/hooks/tools/flatten/useFlattenParameters.ts
@@ -3,10 +3,12 @@ import { useBaseParameters, BaseParametersHook } from '@app/hooks/tools/shared/u
 
 export interface FlattenParameters extends BaseParameters {
   flattenOnlyForms: boolean;
+  renderDpi?: number;
 }
 
 export const defaultParameters: FlattenParameters = {
   flattenOnlyForms: false,
+  renderDpi: undefined,
 };
 
 export type FlattenParametersHook = BaseParametersHook<FlattenParameters>;