请转到pypdf，它本质上与PyPDF2相同，但开发将在那里继续（我是这两个项目的维护者）。
您的问题已在文档中得到解答：

• https://pypdf.readthedocs.io/en/latest/user/streaming-data.html

不是写入文件，而是写入io.ByteIO流：

from io import ByteIO

# e.g. writer = PdfWriter()
# ... do what you want to do with the PDFs

with BytesIO() as bytes_stream:
    writer.write(bytes_stream)
    bytes_stream.seek(0)
    data = bytes_stream.read()  # that is now the "bytes" represention

要合并PDF文件而不将其保存在本地，可以使用requests库下载每个文件的内容，然后将内容传递给PyPDF2库中的PdfFileReader类。

import requests
import PyPDF2
from io import BytesIO

def merge_pdfs_remotely(urls, output_filename):
    # Create a list of file-like objects from the URLs
    file_streams = [BytesIO(requests.get(url).content) for url in urls]
    
    # Create the PDF merger object
    merger = PyPDF2.PdfFileMerger()
    
    # Add each PDF file to the merger
    for stream in file_streams:
        merger.append(PyPDF2.PdfFileReader(stream))