You can manage how Microsoft SharePoint Designer is used at two levels:
Web application level which is applicable to all site collections in the web application and to the site collection administrators.
Site collection level (managed by site collection administrators) which is applicable to all sites in the collection along with the Designers and Owners group.
Note: In SharePoint, only the Designers group and above can open SharePoint sites in SharePoint Designer 2010.
You can control the following types of access to SharePoint Designer 2010 at the site collection level:
Enable SharePoint Designer Enable or disable SharePoint Designer 2010 use for an entire application or site collection. If you want to ensure that all designers and owners within a specific site collection can use SharePoint Designer 2010, enable this setting at the site collection level.
Enable Detaching Pages from the Site Definition Enables or disables the ability to detach pages from the site definition. If you want to preserve the branding for all sites in a site collection, you should not allow users to make changes that would result in detaching the page from the site definition.
Enable Customizing Master Pages and Layout Pages Enables or disables the ability to customize master pages and page layouts. If you do not want users to see the master pages and page layouts for a site, you should disable this setting.
Enable Managing of the Web Site URL StructureEnables or disables the ability to view and edit files in the URL structure of a site. If you do not want users to view and edit any file on the site, you should disable this setting.
When disabled, SharePoint Designer does not display the All Files option in the Navigation panel.
Overall, an user needs to be a member of one of the following groups at the site collection level to be able to use SharePoint Designer and modify SharePoint content:
Site Collection Administrators
Refereed Link :
Check Designer permission regarding issue