Update README.md

README.md

@@ -87,6 +87,12 @@ chown www-data /path/to/folder/to/store/pdf
 
 The digital signature depends on `pdfsig` from the poppler project (poppler-utils debian package) and `certutil` from libnss3 project (libnss3-tools debian package).
 
+On debian :
+
+```
+sudo apt-get install poppler-utils libnss3-tool
+```
+
 To enable digital signature, create certificates in a NSS database. The shell script `create_nss_certs.sh` in `tools` helps to do it :
 
      bash tools/create_nss_certs.sh NSS_DIRECORY/ MY_NSS_PASSWORD MY_CERT_NICK MY_SIGNATUREPDF_URL