What's the maximum number of pages a PDF produced by pdfTeX can have?

pdfTeX

The pages are stored in a page structure, a balanced tree. The top node contains an integer with the number of pages. The maximal integer number in PDF and TeX is 2³¹−1 (2,147,483,647). However indirect objects are needed to store pages in the PDF format (PDF specification):

• 1 Page node per page;
• 1 Resources object per page (pdfTeX generates the object for each page, even if the resource objects are the same and could be shared);
• 1 Contents object per page (in theory equal pages could share the same object, but it is not supported by pdfTeX and unlikely for real documents).
• Overhead of the page tree structure with additional kid nodes;
• And the document has a few additional objects (e.g. Catalog, Info).

Thus more than 3 indirect objects are needed per page. But the number of indirect objects (indirect objects are PDF objects that can be referenced by the object number and are recorded in the cross reference section) is limited: 2²³−1 (8,388,607).

The following test file explores the maximal number of pages with pdfTeX. It does only generates minimal pages without fonts, annotations. The pages are completely empty (\shipout\hbox{}).

% pdftex --ini test.tex
\catcode`\{=1
\catcode`\}=2
\pdfoutput=1
\iffalse
  \pdfobjcompresslevel=2
  \pdfcompresslevel=9
\else
  \pdfobjcompresslevel=0
  \pdfcompresslevel=0
\fi
\pdfminorversion=5
\countdef\pageno=0
\chardef\one=1
\countdef\max=255
\max=2621437
\def\x{%
  \advance\pageno\one
  \shipout\hbox{}%
  \ifnum\max=\pageno
    \let\x\relax
  \fi
  \x
}
\x
\end

Tested with pdfTeX 3.1415925-2.4-1.40.13 (TeX Live 2012). Result:

Pages: 2,621,437
File size: 862,082,448 bytes
PDF without object stream compression

If the page number is increased by one, then pdfTeX complains with an error message:

! TeX capacity exceeded, sorry [indirect objects table size=8388607].

PDF object stream compression of PDF-1.5 decreases the file size, but costs indirect objects for storing the object streams. That decreases the maximal number of pages. For testing, replace \iffalse by \iftrue in the example above and play with the setting for \max. Result:

Pages: 2,603,538
File size: 329,412,496
PDF with object stream compression

In practice especially annotations costs objects (and therefore pages), whereas fonts can be reused throughout the document.

Summary

The theoretical maximal number of pages for PDF files with pdfTeX is 2,621,437 (empty pages and without object stream compression of PDF-1.5).

LuaTeX 0.95.0

LuaTeX derived from pdfTeX, thus the empty page uses the same number of objects as in the case of pdfTeX. The page tree is stored with less number of objects, because pdfTeX uses 6 kids in a page tree node, but LuaTeX has increased the number to 10 kids per page tree node.

Therefore, LuaTeX can create a little more pages. The hard limitation is the number of indirect objects in the PDF file (2²³-1).

Test file for LuaTeX 0.95.0 with option --ini:

\catcode`\{=1
\catcode`\}=2
\directlua{tex.enableprimitives("",{"outputmode"})}
\outputmode=1
\directlua{
  \iffalse
     pdf.setobjcompresslevel(2)
     pdf.setcompresslevel(9)
  \else
    pdf.setobjcompresslevel(0)
    pdf.setcompresslevel(0)
  \fi
  pdf.setminorversion(5)
}
\countdef\pageno=0
\chardef\one=1
\countdef\max=255
\max=2696336
\def\x{%
  \advance\pageno\one
  \shipout\hbox{}%
  \ifnum\max=\pageno
    \let\x\relax
  \fi
  \x
}
\x
\end

Result:

Pages: 2,696,336
File size: 821,034,398 bytes
PDF without object stream compression

Summary

LuaTeX can generate a PDF document with 2,696,336 empty pages.

XeTeX

XeTeX uses the program xdvipdfmx as output driver for PDF. It generates the PDF file with empty pages in a similar way as pdfTeX or LuaTeX. However, it uses more nodes (indirect objects) for the page tree than the other TeX compilers. The LuaTeX run with 2,400,000 pages took nearly a minute, but the XeTeX run about 18 minutes.

Test file:

\catcode`\{=1
\catcode`\}=2
\countdef\pageno=0
\chardef\one=1
\countdef\max=255
\max=2400000
\def\x{%
  \advance\pageno\one
  \shipout\hbox{}%
  \ifnum\max=\pageno
    \let\x\relax
  \fi
  \x
}
\x
\end

Command call with options to turn compression off:

xetex -ini -output-driver="xdvipdfmx -C 0x0040 -z 0" test.tex

2,400,001 pages generate the error message:

xdvipdfmx:fatal: Page number 2400002l too large!

File size with 2,400,000 empty pages: 901,335,935 bytes

Version of XeTeX is 3.14159265-2.6-0.99996 (TeX Live 2016) and the version of xdvipdfmx is 20160307.

Summary

XeTeX can generate a PDF document with 2,400,000 empty pages, but it is much slower than pdfTeX or LuaTeX.

TeX is designed to have very limited memory requirements (basically once a page is shipped out it is gone) I had people generating longtable documents with 10s of thousands of pages back in the 1990's so on modern machines I don't think 170 pages is going to stress the system too much.

What is more important than page count is page complexity: if you have a high resolution plot done in tikz or picture mode or some such then that ends up being an awful lot of boxes on the same page. That's why sometimes it helps to generate such things as external graphics to be included. Unless they are changing on each run that will typically speed things up even if calculating them inline doesn't exceed memory requirements.

Other than architectural limits of PDF (the number of indirect objects in a PDF is limited to 8Mi as per ISO-32000:2008, and numbers are limited to 2Gi), there are no known limits. If memory allows and your disc is large enough, pdfTeX should be able to generate PDF up to some TiBytes. It will fail eventually—the offset size in the compressed xref table is currently limited to 2⁴⁰(5 bytes)—but extending that limit is easy.