diff --git a/plugins/webp-uploads/helper.php b/plugins/webp-uploads/helper.php
index a089809361..7d2b1249b5 100644
--- a/plugins/webp-uploads/helper.php
+++ b/plugins/webp-uploads/helper.php
@@ -29,10 +29,11 @@ function webp_uploads_get_upload_image_mime_transforms(): array {
 	$output_format = webp_uploads_mime_type_supported( 'image/avif' ) ? webp_uploads_get_image_output_format() : 'webp';
 
 	$default_transforms = array(
-		'image/jpeg' => array( 'image/' . $output_format ),
-		'image/webp' => array( 'image/' . $output_format ),
-		'image/avif' => array( 'image/avif' ),
-		'image/png'  => array( 'image/' . $output_format ),
+		'image/jpeg'      => array( 'image/' . $output_format ),
+		'image/webp'      => array( 'image/' . $output_format ),
+		'image/avif'      => array( 'image/avif' ),
+		'image/png'       => array( 'image/' . $output_format ),
+		'application/pdf' => array( 'image/' . $output_format ),
 	);
 
 	// Check setting for whether to generate both JPEG and the modern output format.
@@ -144,7 +145,11 @@ function webp_uploads_generate_additional_image_source( int $attachment_id, stri
 		return new WP_Error( 'image_mime_type_not_supported', __( 'The provided mime type is not supported.', 'webp-uploads' ) );
 	}
 
-	$image_path = wp_get_original_image_path( $attachment_id );
+	if ( wp_attachment_is_image( $attachment_id ) ) {
+		$image_path = wp_get_original_image_path( $attachment_id );
+	} else {
+		$image_path = get_attached_file( $attachment_id );
+	}
 	if ( false === $image_path || ! file_exists( $image_path ) ) {
 		return new WP_Error( 'original_image_file_not_found', __( 'The original image file does not exists, subsizes are created out of the original image.', 'webp-uploads' ) );
 	}
diff --git a/plugins/webp-uploads/tests/test-helper.php b/plugins/webp-uploads/tests/test-helper.php
index 0eaa68e74a..79292dd6c3 100644
--- a/plugins/webp-uploads/tests/test-helper.php
+++ b/plugins/webp-uploads/tests/test-helper.php
@@ -414,17 +414,19 @@ public function test_it_should_return_default_transforms_when_filter_returns_non
 		if ( webp_uploads_mime_type_supported( 'image/avif' ) ) {
 			$this->set_image_output_type( 'avif' );
 			$default_transforms = array(
-				'image/jpeg' => array( 'image/avif' ),
-				'image/webp' => array( 'image/avif' ),
-				'image/avif' => array( 'image/avif' ),
-				'image/png'  => array( 'image/avif' ),
+				'image/jpeg'      => array( 'image/avif' ),
+				'image/webp'      => array( 'image/avif' ),
+				'image/avif'      => array( 'image/avif' ),
+				'image/png'       => array( 'image/avif' ),
+				'application/pdf' => array( 'image/avif' ),
 			);
 		} else {
 			$default_transforms = array(
-				'image/jpeg' => array( 'image/webp' ),
-				'image/webp' => array( 'image/webp' ),
-				'image/avif' => array( 'image/avif' ),
-				'image/png'  => array( 'image/webp' ),
+				'image/jpeg'      => array( 'image/webp' ),
+				'image/webp'      => array( 'image/webp' ),
+				'image/avif'      => array( 'image/avif' ),
+				'image/png'       => array( 'image/webp' ),
+				'application/pdf' => array( 'image/webp' ),
 			);
 		}
 
@@ -500,6 +502,16 @@ public function test_it_should_return_jpeg_and_webp_transforms_when_option_gener
 		}
 	}
 
+	/**
+	 * Returns true if 'application/pdf' is included in the MIME transforms array.
+	 */
+	public function test_it_should_include_pdf_in_mime_transforms(): void {
+		$transforms = webp_uploads_get_upload_image_mime_transforms();
+
+		$this->assertArrayHasKey( 'application/pdf', $transforms );
+		$this->assertContains( 'image/webp', $transforms['application/pdf'] );
+	}
+
 	/**
 	 * @dataProvider data_provider_image_filesize
 	 *