diff --git a/API.md b/API.md
index 5498661..9098ebd 100644
--- a/API.md
+++ b/API.md
@@ -70,7 +70,8 @@ Name | Type | Attributes | Description
 --- | --- | --- | ---
 text | string | required | A text to draw.
 size | number | required | Font size
-fontData | Array\<number\><br />:fork_and_knife:Uint8Array<br />:fork_and_knife:ArrayBuffer<br />:fork_and_knife:string | optional | The font's data for drawing text.<br />If it is a string, it is assumed to be one of the values in [PDFLib.StandardFonts](https://pdf-lib.js.org/docs/api/enums/standardfonts)<br />Default: `StandardFonts.Helvetica`
+fontData | Array\<number\><br />:fork_and_knife:Uint8Array<br />:fork_and_knife:ArrayBuffer<br />:fork_and_knife:[PDFLib.StandardFonts](https://pdf-lib.js.org/docs/api/enums/standardfonts) | optional | The font's data for drawing text.<br />See [PdfFonts.getEmbeddedFont](#getEmbeddedFont) for the default font.
+subset | boolean | optional | Create font subset or not.<br />Set to true to reduce the size of pdf file.
 color | string | optional | A Hex string of font color. :one:<br />Default: `#000`
 opacity | number | optional | Valid value is from 0 to 1.<br />Default: `1`<br />:no_entry_sign:<ins>Not implemented yet</ins>
 blendMode | string | optional | Valid value is one of the values in [PDFLib.BlendMode](https://pdf-lib.js.org/docs/api/enums/blendmode)<br />:no_entry_sign:<ins>Not implemented yet</ins>
@@ -257,7 +258,7 @@ sign(pdf, cypopt<sub>*opt*</sub>) :arrow_right: Promise\<Uint8Array\>
 Sign the pdf and returns the binary data.
 Name | Type | Attributes | Description
 --- | --- | --- | ---
-pdf | PDFLib.PDFDocument|Array\<number\>|Uint8Array|ArrayBuffer|string | required | The target pdf.
+pdf | PDFLib.PDFDocument<br />:fork_and_knife:Array\<number\><br />:fork_and_knife:Uint8Array<br />:fork_and_knife:ArrayBuffer<br />:fork_and_knife:string | required | The target pdf.
 cypopt | [EncryptOption](#EncryptOption) | optional | The informations of encryption.
 
 ## TsaFetcher
@@ -293,6 +294,25 @@ Name | Type | Attributes | Description
 --- | --- | --- | ---
 data | string | required | The data needs to be signed.
 
+## PdfFonts
+:croissant::croissant::croissant:
+### Static Methods
+#### from
+from(pdfdoc) :arrow_right: Promise\<[PdfFonts](#PdfFonts)\>  
+Load embedded fonts from pdf document.
+Name | Type | Attributes | Description
+--- | --- | --- | ---
+pdfdoc | PDFLib.PDFDocument | required | The target pdf document.
+
+### Methods
+#### getEmbeddedFont
+getEmbeddedFont(fontData<sub>*opt*</sub>, subset<sub>*opt*</sub>) :arrow_right: Promise\<PDFLib.PDFFont\>  
+Get the embedded font or create one if not exists.
+Name | Type | Attributes | Description
+--- | --- | --- | ---
+fontData | Array\<number\><br />:fork_and_knife:Uint8Array<br />:fork_and_knife:ArrayBuffer<br />:fork_and_knife:[PDFLib.StandardFonts](https://pdf-lib.js.org/docs/api/enums/standardfonts) | optional | Data of font. If omitted,<br />the default font is `PDFLib.StandardFonts.Helvetica` if there is no existing embedded font.<br />Or the default font is the first existing embedded font.
+subset | boolean | optional | Create font subset or not.
+
 ## Note
 * __CRL__:loudspeaker: Certificate Revocation List
 * __DSS__:loudspeaker: Document Security Store