diff --git a/README.md b/README.md
index fecce1e..aed6540 100644
--- a/README.md
+++ b/README.md
@@ -57,6 +57,7 @@ This Python library is designed for testing the OData API of Creatio. It include
   - [Get Data from a Collection](#get-data-from-a-collection)
   - [Delete a Record from a Collection](#delete-a-record-from-a-collection)
   - [Handle information from the API session](#handle-information-from-the-api-session)
+  - [Download a file from a Collection's attachments](#download-a-file-from-a-collections-attachments)
 - [Contributors](#contributors)
   - [How do I contribute to creatio-api-py?](#how-do-i-contribute-to-creatio-api-py)
 - [License](#license)
@@ -335,6 +336,23 @@ Additionally, you can modify the object's base url if needed:
 api.base_url = "https://another-environment.creatio.com"
 ```
 
+## Download a file from a Collection's attachments
+
+```python
+file_id = "9dc61894-a14c-dff5-b4ff-6bca9a26018d"
+api.download_file("ContactFile", file_id=file_id)
+```
+
+- Response code: `200 OK`
+- Response body: The file content
+
+Additionally, you can specify the path where the file will be saved:
+
+```python
+file_id = "9dc61894-a14c-dff5-b4ff-6bca9a26018d"
+api.download_file("ContactFile", file_id=file_id, path="path/to/save/file")
+```
+
 # Contributors
 
 <a href="https://github.com/YisusChrist/creatio-api-py/graphs/contributors"><img src="https://contrib.rocks/image?repo=YisusChrist/creatio-api-py" /></a>
diff --git a/creatio_api_py/api.py b/creatio_api_py/api.py
index c47634a..aff621f 100644
--- a/creatio_api_py/api.py
+++ b/creatio_api_py/api.py
@@ -166,6 +166,7 @@ def _make_request(
         self,
         method: str,
         endpoint: str,
+        headers: Optional[dict[str, str]] = None,
         **kwargs: Any,
     ) -> requests.models.Response:
         """
@@ -180,7 +181,9 @@ def _make_request(
             requests.models.Response: The response from the HTTP request.
         """
         url: str = f"{self.base_url}{endpoint}"
-        headers: dict[str, str] = self._build_headers(endpoint, method)
+        if not headers:
+            headers = {}
+        headers.update(self._build_headers(endpoint, method))
 
         try:
             response: requests.Response = self.__session.request(
@@ -457,3 +460,70 @@ def download_file(
             f.write(response.content)
 
         return response
+
+    def upload_file(
+        self, collection: str, entity_id: str, file_path: str | Path
+    ) -> requests.models.Response:
+        """
+        Upload a file to Creatio.
+
+        Args:
+            collection (str): The collection to upload the file to.
+            entity_id (str): The ID of the entity to associate the file with.
+            file_path (str | Path): The path to the file to upload.
+
+        Returns:
+            requests.models.Response: The response from the file upload request.
+        """
+        # Read the file data to ensure the file is valid
+        file_path = file_path if isinstance(file_path, Path) else Path(file_path)
+        with open(file_path, "rb") as f:
+            data: bytes = f.read()
+
+        file_length: int = len(data)
+        parent_collection: str = collection[: -len("File")]
+
+        # Create the file in the collection table
+        payload: dict[str, Any] = {
+            "Name": file_path.name,
+            f"{parent_collection}Id": entity_id,
+            "Size": file_length,
+            "TotalSize": file_length,
+            "TypeId": "529bc2f8-0ee0-df11-971b-001d60e938c6",
+        }
+        response: requests.Response = self.add_collection_data(collection, data=payload)
+        response.raise_for_status()
+
+        # Get the file ID from the response
+        file_id: str = response.json().get("Id")
+        if not file_id:
+            raise ValueError("Could not determine the file ID from the response")
+
+        content_type = "application/pdf"
+        params: dict[str, str | int] = {
+            "fileId": file_id,
+            "totalFileLength": file_length,
+            #"mimeType": content_type,
+            "fileName": file_path.name,
+            "columnName": "Data",
+            "entitySchemaName": collection,
+            "parentColumnName": parent_collection,
+            "parentColumnValue": entity_id,
+        }
+
+        headers: dict[str, str] = {
+            "Content-Type": content_type,
+            "Content-Disposition": f"attachment; filename={file_path.name}",
+        }
+
+        # TODO: Fix this call, currently returns a InvalidFileSizeException error
+        # Probably related to content-type header and mimeType value
+        response = self._make_request(
+            "POST",
+            f"0/rest/FileApiService/UploadFile",
+            params=params,
+            data=data,
+        )
+        response.raise_for_status()
+
+        return response
diff --git a/pyproject.toml b/pyproject.toml
index 5c1dc4b..b40b5be 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,6 +1,6 @@
 [project]
 name = "creatio-api-py"
-version = "1.3.0"
+version = "1.3.1"
 description = "Python client for Creatio OData API"
 authors = [
     { name = "Alejandro González Momblán", email = "alejandro.gonzalez.momblan@evoluciona.es" },