diff --git a/konova/forms.py b/konova/forms.py
index 95cf5902..359b78bc 100644
--- a/konova/forms.py
+++ b/konova/forms.py
@@ -354,7 +354,7 @@ class NewDocumentForm(BaseModalForm):
     file = forms.FileField(
         label=_("File"),
         label_suffix=_(""),
-        help_text=_("Must be smaller than 15 Mb"),
+        help_text=_("Allowed formats: pdf, jpg, png. Max size 15 MB."),
         widget=forms.FileInput(
             attrs={
                 "class": "form-control-file",
@@ -391,6 +391,28 @@ class NewDocumentForm(BaseModalForm):
         if not self.document_model:
             raise NotImplementedError("Unsupported document type for {}".format(self.instance.__class__))
 
+    def is_valid(self):
+        super_valid = super().is_valid()
+
+        _file = self.cleaned_data.get("file", None)
+
+        mime_type_valid = self.document_model.is_mime_type_valid(_file)
+        if not mime_type_valid:
+            self.add_error(
+                "file",
+                _("Unsupported file type")
+            )
+
+        file_size_valid = self.document_model.is_file_size_valid(_file)
+        if not file_size_valid:
+            self.add_error(
+                "file",
+                _("File too large")
+            )
+
+        file_valid = mime_type_valid and file_size_valid
+        return super_valid and file_valid
+
     def save(self):
         with transaction.atomic():
             action = UserActionLogEntry.get_created_action(self.user)
diff --git a/konova/models/document.py b/konova/models/document.py
index 11b6c06d..72b124d3 100644
--- a/konova/models/document.py
+++ b/konova/models/document.py
@@ -5,6 +5,7 @@ Contact: michel.peltriaux@sgdnord.rlp.de
 Created on: 15.11.21
 
 """
+import mimetypes
 import os
 
 from django.db import models
@@ -62,6 +63,15 @@ class AbstractDocument(BaseResource):
     file = models.FileField()
     comment = models.TextField()
 
+    _valid_mime_types = {
+        mimetypes.types_map[".pdf"],
+        mimetypes.types_map[".jpg"],
+        mimetypes.types_map[".jpeg"],
+        mimetypes.types_map[".png"],
+    }
+    # _maximum_file_size in MB
+    _maximum_file_size = 15
+
     class Meta:
         abstract = True
 
@@ -82,3 +92,12 @@ class AbstractDocument(BaseResource):
             pass
         super().delete(using=using, keep_parents=keep_parents)
 
+    @classmethod
+    def is_mime_type_valid(cls, _file: str):
+        mime_type = _file.content_type
+        return mime_type in cls._valid_mime_types
+
+    @classmethod
+    def is_file_size_valid(cls, _file):
+        max_size = cls._maximum_file_size * pow(1000, 2)
+        return _file.size <= max_size
diff --git a/konova/tests/test_documents.py b/konova/tests/test_documents.py
new file mode 100644
index 00000000..e1f800e0
--- /dev/null
+++ b/konova/tests/test_documents.py
@@ -0,0 +1,73 @@
+"""
+Author: Michel Peltriaux
+Organization: Struktur- und Genehmigungsdirektion Nord, Rhineland-Palatinate, Germany
+Contact: michel.peltriaux@sgdnord.rlp.de
+Created on: 09.12.21
+
+"""
+import mimetypes
+
+from django.core.files.uploadedfile import InMemoryUploadedFile
+
+from konova.models import AbstractDocument
+from konova.tests.test_views import BaseTestCase
+
+
+class TestCaseDocuments(BaseTestCase):
+    """
+    Tests for the Documents functionalities
+    """
+
+    @classmethod
+    def setUpTestData(cls):
+        """ Creates a test file in memory for using in further tests
+
+        Returns:
+
+        """
+        super().setUpTestData()
+        cls.max_file_size = AbstractDocument._maximum_file_size * pow(1000, 2)
+        cls.test_file = InMemoryUploadedFile(
+            charset="utf-8",
+            name="test_file",
+            size=cls.max_file_size,
+            file=None,
+            content_type=None,
+            field_name=None
+        )
+
+    def test_allowed_mime_types(self):
+        """ Unit test for mime type validity checker
+
+        Checks that only as acceptable configured mime types of an AbstractDocument object will pass the
+        validity check.
+
+        Returns:
+
+        """
+        accepted_mime_types = []
+        for file_ending, mime_type in mimetypes.types_map.items():
+            self.test_file.content_type = mime_type
+            valid = AbstractDocument.is_mime_type_valid(self.test_file)
+            if valid:
+                accepted_mime_types.append(mime_type)
+        accepted_mime_types = set(accepted_mime_types)
+
+        self.assertEqual(accepted_mime_types, AbstractDocument._valid_mime_types)
+
+    def test_max_file_size(self):
+        """ Unit test for maximum file size validity checker
+
+        Returns:
+
+        """
+        # Test for exact maximum size
+        self.assertTrue(AbstractDocument.is_file_size_valid(self.test_file))
+
+        # Test for lower than maximum size
+        self.test_file.size = self.max_file_size - 1
+        self.assertTrue(AbstractDocument.is_file_size_valid(self.test_file))
+
+        # Test for larger than maximum size
+        self.test_file.size = self.max_file_size + 1
+        self.assertFalse(AbstractDocument.is_file_size_valid(self.test_file))
diff --git a/locale/de/LC_MESSAGES/django.mo b/locale/de/LC_MESSAGES/django.mo
index d5e0cf26..bea21be2 100644
Binary files a/locale/de/LC_MESSAGES/django.mo and b/locale/de/LC_MESSAGES/django.mo differ
diff --git a/locale/de/LC_MESSAGES/django.po b/locale/de/LC_MESSAGES/django.po
index 83f193bb..b194437a 100644
--- a/locale/de/LC_MESSAGES/django.po
+++ b/locale/de/LC_MESSAGES/django.po
@@ -19,7 +19,7 @@ msgid ""
 msgstr ""
 "Project-Id-Version: PACKAGE VERSION\n"
 "Report-Msgid-Bugs-To: \n"
-"POT-Creation-Date: 2021-11-17 14:27+0100\n"
+"POT-Creation-Date: 2021-12-09 12:36+0100\n"
 "PO-Revision-Date: YEAR-MO-DA HO:MI+ZONE\n"
 "Last-Translator: FULL NAME <EMAIL@ADDRESS>\n"
 "Language-Team: LANGUAGE <LL@li.org>\n"
@@ -1311,7 +1311,7 @@ msgstr "Datum des Widerspruchs"
 msgid "Document"
 msgstr "Dokument"
 
-#: intervention/forms/modalForms.py:140 konova/forms.py:357
+#: intervention/forms/modalForms.py:140
 msgid "Must be smaller than 15 Mb"
 msgstr "Muss kleiner als 15 Mb sein"
 
@@ -1333,7 +1333,7 @@ msgstr "Kompensationen und Zahlungen geprüft"
 msgid "Run check"
 msgstr "Prüfung vornehmen"
 
-#: intervention/forms/modalForms.py:196 konova/forms.py:429
+#: intervention/forms/modalForms.py:196 konova/forms.py:451
 msgid ""
 "I, {} {}, confirm that all necessary control steps have been performed by "
 "myself."
@@ -1559,27 +1559,39 @@ msgstr "Wann wurde diese Datei erstellt oder das Foto aufgenommen?"
 msgid "File"
 msgstr "Datei"
 
-#: konova/forms.py:397
+#: konova/forms.py:357
+msgid "Allowed formats: pdf, jpg, png. Max size 15 MB."
+msgstr "Formate: pdf, jpg, png. Maximal 15 MB."
+
+#: konova/forms.py:403
+msgid "Unsupported file type"
+msgstr "Dateiformat nicht unterstützt"
+
+#: konova/forms.py:410
+msgid "File too large"
+msgstr "Datei zu groß"
+
+#: konova/forms.py:419
 msgid "Added document"
 msgstr "Dokument hinzugefügt"
 
-#: konova/forms.py:420
+#: konova/forms.py:442
 msgid "Confirm record"
 msgstr "Verzeichnen bestätigen"
 
-#: konova/forms.py:428
+#: konova/forms.py:450
 msgid "Record data"
 msgstr "Daten verzeichnen"
 
-#: konova/forms.py:435
+#: konova/forms.py:457
 msgid "Confirm unrecord"
 msgstr "Entzeichnen bestätigen"
 
-#: konova/forms.py:436
+#: konova/forms.py:458
 msgid "Unrecord data"
 msgstr "Daten entzeichnen"
 
-#: konova/forms.py:437
+#: konova/forms.py:459
 msgid "I, {} {}, confirm that this data must be unrecorded."
 msgstr ""
 "Ich, {} {}, bestätige, dass diese Daten wieder entzeichnet werden müssen."
@@ -3182,6 +3194,9 @@ msgstr ""
 msgid "A fontawesome icon field"
 msgstr ""
 
+#~ msgid "No file given!"
+#~ msgstr "Keine Datei angegeben!"
+
 #~ msgid "Added payment"
 #~ msgstr "Zahlung hinzufügen"