Adds HMD_ALLOW_PDF_EXPORT to readme

Author: dilpreetsio

README.md

@@ -145,9 +145,10 @@ Environment variables (will overwrite other server configs)
 | HMD_LDAP_SEARCHFILTER | `(uid={{username}})` | LDAP filter to search with |
 | HMD_LDAP_SEARCHATTRIBUTES | no example | LDAP attributes to search with |
 | HMD_LDAP_TLS_CA | `server-cert.pem, root.pem` | Root CA for LDAP TLS in PEM format (use comma to separate) |
-| HMD_LDAP_PROVIDERNAME | `My institution` | Optional name to be displayed at login form indicating the LDAP provider | 
+| HMD_LDAP_PROVIDERNAME | `My institution` | Optional name to be displayed at login form indicating the LDAP provider |
 | HMD_IMGUR_CLIENTID | no example | Imgur API client id |
 | HMD_EMAIL | `true` or `false` | set to allow email signin |
+| HMD_ALLOW_PDF_EXPORT | `true` or `false` | Enable or disable PDF exports |
 | HMD_ALLOW_EMAIL_REGISTER | `true` or `false` | set to allow email register (only applied when email is set, default is `true`) |
 | HMD_IMAGE_UPLOAD_TYPE | `imgur`, `s3` or `filesystem` | Where to upload image. For S3, see our [S3 Image Upload Guide](docs/guides/s3-image-upload.md) |
 | HMD_S3_ACCESS_KEY_ID | no example | AWS access key id |