Use this code example to add custom CSS to your PDF. The $css variable will return all the custom CSS from the PHP function into the stylesheet for the PDF using the following expression:

<style type="text/css">' . $css . '</style>

In the line where it says, Modify the CSS here, add your custom CSS.

add_filter('frm_pdfs_css', 'modify_pdfs_css' , 10, 2);

function modify_pdfs_css( $css, $args ) {

	// Modify the CSS here.

	return $css;

}

Note: CSS customization is fairly limited. Because the PDF libraries do not support all CSS rules, it is best to keep things simple.

By default, PDF files use font defined in Styles settings. If your language texts don't display correctly in the PDF file, you need to use a different font that supports your language. PDFs addon contains built-in Dejavu Sans font, which supports some languages like Hebrew, Polish, etc.... Use the following code snippet to use the Dejavu Sans font.

add_filter('frm_pdfs_css', 'custom_font_pdfs_css', 10, 2);

function custom_font_pdfs_css( $css, $args ) {

	$custom_css = 'body { font-family: Dejavu Sans, sans-serif; }';

	return $css . $custom_css;

}

If the Dejavu Sans font doesn't help, you must find another font and register it using CSS @font-face. You need a .ttf file (true type font) that can be accessed via a URL. Use the following example to add the Seto font, which we found to support most languages.

add_filter('frm_pdfs_css', 'ttf_font_pdfs_css', 10, 2);
function ttf_font_pdfs_css( $css, $args ) {
	$custom_css = "
		@font-face {
			font-family: 'Seto';
			font-style: normal;
			font-weight: normal;
			src: url(https://github.com/googlefonts/chinese/raw/gh-pages/fonts/SetoFont/setofont.ttf) format('truetype');
		}

		body {
			font-family: Seto, sans-serif;
		}
	";
	return $css . $custom_css;
}

• font-style and font-weight should match your text styling. For example, if your text is bold italic, you need to add another @font-face with font-style: italic and font-weight: bold.
• When a PDF file is generated for the first time, that .ttf file will be downloaded to the wp-content/uploads folder (you can change this location with the frm_pdfs_dompdf_args filter). So you will see that it is slower. After that, it will use the downloaded file, and you can remove the added @font-face in the custom code.
• We suggest uploading the custom font files to your server, allowing them to be accessed through a URL. Occasionally, external links may not function properly.

If you don't want to apply the custom font to the whole PDF file, use the following code example to replace body with any CSS selector you want.

add_filter('frm_pdfs_css', 'custom_font_pdfs_css_selector',10, 2);

function custom_font_pdfs_css_selector( $css, $args ) {

	$custom_css = '.custom-language-text { font-family: Dejavu Sans, sans-serif; }';

	return $css . $custom_css;

}

Use the following code example to apply the custom font for specific entries. It is useful if you have a multi languages site.

add_filter('frm_pdfs_css', 'custom_font_pdfs_css_entry' ,10, 2);
function custom_font_pdfs_css_entry( $css, $args ) {
	if ( empty( $args['id'] ) ) { // Check for entry ID.
		return $css;
	}

	if ( is_secondary_language_view( $args['id'] ) ) {
		return $css;
	}

	$custom_css = 'body { font-family: Dejavu Sans, sans-serif; }';
	return $css . $custom_css;
}

Use the following example to add fonts from the Chinese language. You can register it using @import and will need a .ttf file that can be accessed via a URL.

add_filter('frm_pdfs_css', 'ttf_font_pdfs_css', 10, 2);
function ttf_font_pdfs_css($css, $args) {
    $custom_css = "
        @import url('https://fonts.googleapis.com/css2?family=Noto+Serif+SC:wght@200..900&display=swap');

        body {
            font-family: \"Noto Serif SC\", sans-serif;
            font-optical-sizing: auto;
            font-style: normal;
        }
    ";

    return $css . $custom_css;
}