import arcpy, os

# Set the workspace.
arcpy.env.workspace = r"C:Output"

#Set file name and remove if it already exists
pdfPath = r"C:OutputMap.pdf"
if os.path.exists(pdfPath):
    os.remove(pdfPath)

# List all of the pdf files in the output folder.
# pdfList is a Python List returned from the ListFiles function.
pdfList = arcpy.ListFiles("*.pdf")

#Create the file and append pages
pdfDoc = arcpy.mp.PDFDocumentCreate(pdfPath)

for f in pdfList:
    pdfDoc.appendPages(f)

pdfDoc.saveAndClose()

del pdfDoc

import os
for f in pdfList:
    pdfDoc.appendPages(os.path.join (r"C:Output", f))