SigningHub offers multilingual interface to facilitate its worldwide customers to send documents for signature in their native language. In this regard, you can change the entire GUI of your SigningHub for SharePoint as per your desired language. 
The system supports more than 20 international languages, i.e.:

•  "en-US" : "English",
•   "nl-NL" : "Nederlands",
•   "es-ES" : "Español (ES)",
•   "es-LA" : "Español (LA)",
•   "fr-FR" : "Français",
•   "de-DE" : "Deutsch",
•   "ar-AE" : "العربية",
•   "tr-TR" : "Türkçe",
•   "lv-LV" : "Latviski",
•   "nb-NO" : "Norsk",
•   "el-GR" : "ελληνικά",
•   "hi-IN" : "हिंदी",
•   "id-ID" : "Bahasa Indonesia",
•   "ja-JP" : "日本語",
•   "pt-Pt" : "Português (PT)",
•   "pt-BR" : "Português (Brasil)",
•   "ro-RO" : "Română",
•   "ru-RU" : "Pусский",
•   "sr-CR" : "Srpski",
•   "th-TH" : "ภาษาไทย",
•   "vi-VN" : "Tiếng Việt",
•   "zh-CN" : "简体中文",

When you change the display language of your SharePoint account, the same changes will automatically reflect on the SigningHub add-in interface as well, provided your selected language is supported in SigningHub. There are three areas in your SharePoint account to change the display language, i.e.:

• The "Regional Settings" of your SharePoint site on which SigningHub is installed
• The "Language Settings" of your SharePoint site on which SigningHub is installed
• After configuring above two settings, change language settings in your your personal profile accordingly

Configure the Regional Settings of your SharePoint account 

1. Browse the SharePoint site link (on which SigningHub add-in is installed) and log into your Office 365 account with SharePoint administrator credentials.
2. Click  and select the "Site settings" option.
   
   
   
   
3. Click the "Regional Settings" option.
   
   
   
   
4. Change the "Time Zone" and "Locale" fields as required.
5. Click OK.
   
   
   

The entire GUI language of your SharePoint account including SigningHub for SharePoint will be changed accordingly.