It says "Input pdf "filename.pdf" is not valid, when ran as an .exe

### Bug

I have four python files out of which one contains the docling library and a user defined function which extracts the pdf content to markdown.

```python
def convert_pdf_to_text(pdf_path, callback=None, should_stop=None):
"""Convert PDF to text using docling library."""
try:
if should_stop and should_stop():
print_message("PDF conversion cancelled", callback)
return None

pipeline_options = PdfPipelineOptions(
enable_ocr=True,
do_table_structure=True,
detect_language=True,
layout_mode="accurate"
)

if should_stop and should_stop():
print_message("PDF conversion cancelled", callback)
return None

converter = DocumentConverter(format_options={
InputFormat.PDF: PdfFormatOption(pipeline_options=pipeline_options)
})

if should_stop and should_stop():
print_message("PDF conversion cancelled", callback)
return None

print_message(str(pdf_path), callback)

result = converter.convert(pdf_path)

if should_stop and should_stop():
print_message("PDF conversion cancelled", callback)
return None

return result.document.export_to_markdown()

except Exception as e:
print_message(str(pdf_path), callback)
print_message(f"Error during PDF conversion: {str(e)}", callback)
return None
````

This file called from main.py. If I run main.py the program is running without any issues, but if convert it using pyinstaller as exe and I run it then it says : Input pdf "filename.pdf" is not valid.

I converted the program to exe using the following command
pyinstaller --onefile --noconsole main.py

### Steps to reproduce

...

### Docling version

docling 2.36.0

### Python version

python 3.12.10