public class PDF_Class {

    public void insertpdf() {
        
        Contact a = new Contact();
        a.lastname = 'test-foram3';
        insert a;
        
        blob filebody; //set your filebody here
        String fname = 'Resume.pdf';
        ContentVersion conVer = new ContentVersion();
        conVer.ContentLocation = 'S'; // S specify this document is in SF, use E for external files
        conVer.PathOnClient = fname; // The files name, extension is very important here which will help the file in preview.
        conVer.Title = fname; // Display name of the files
        conVer.VersionData = filebody; // converting your binary string to Blog
        insert conVer;  
        
        // First get the content document Id from ContentVersion
        Id conDoc = [SELECT ContentDocumentId FROM ContentVersion WHERE Id =:conVer.Id].ContentDocumentId;
        
        //Create ContentDocumentLink
        ContentDocumentLink cDe = new ContentDocumentLink();
        cDe.ContentDocumentId = conDoc;
        cDe.LinkedEntityId = a.Id; // you can use objectId,GroupId etc
        cDe.ShareType = 'V'; // Inferred permission, checkout description of ContentDocumentLink object for more details
        cDe.Visibility = 'AllUsers';
        insert cDe;
        
        
        
        
        

    }
    
}