import os
from pypdf import PdfMerger
import re

def find_pdf_files(directory):
    pdf_files = []
    for root, _, files in os.walk(directory):
        for file in files:
            if file.endswith('.pdf'):
                file_path = os.path.join(root, file)
                pdf_files.append(file_path)
                print(f'added {str(file)} to the list')
    return pdf_files

pdfs = find_pdf_files(os.getcwd())
pdfs = pdf_files_sorted = sorted(pdfs, key=lambda x: [int(s) if s.isdigit() else s.lower() for s in re.split(r'(\d+)', x)])

merger = PdfMerger()

print('merging...')
for pdf in pdfs:
    print(f'merged {pdf}.')
    merger.append(pdf)

merger.write("merged.pdf")
merger.close()