Contents of outfolder should not be deleted at beginning of watermark

Since some contents of the output folder (pdfs_watermarked) of watermark.py could be valuable, the contents of the output folder should not be completele deleted at the beginning.

.gitlab-ci.yml

-image: docker:19.03.1
-services:
-  - docker:19.03.1-dind
-
-stages:
-  - build-docker
-  - test
-
-variables:
-  GIT_SUBMODULE_STRATEGY: recursive
-  DOCKER_TLS_CERTDIR: "/certs"
-  DOCKER_HOST: tcp://docker:2376 # Use TLS https://docs.gitlab.com/ee/ci/docker/using_docker_build.html#tls-enabled
-
-before_script:
-  - docker login -u ${CI_REGISTRY_USER} -p ${CI_REGISTRY_PASSWORD} ${CI_REGISTRY}
-
-build:
-  stage: build-docker
-  script:
-    - docker pull ${CI_REGISTRY_IMAGE}:latest || true
-    - docker build --cache-from ${CI_REGISTRY_IMAGE}:latest
-                   --tag ${CI_REGISTRY_IMAGE}:${CI_COMMIT_REF_SLUG}
-                   --tag ${CI_REGISTRY_IMAGE}:latest .
-    - docker push ${CI_REGISTRY_IMAGE}:${CI_COMMIT_REF_SLUG}
-    - docker push ${CI_REGISTRY_IMAGE}:latest
-
-    
-test:
-  stage: test
-  script:
-    - docker run --name examscan --rm -v $(pwd):$(pwd) -w $(pwd) ${CI_REGISTRY_IMAGE}:latest --in pdfs --out out --tmp tmp
-  artifacts:
-    paths:
-    - out/
\ No newline at end of file