The symbol is in Unicode

U+267E PERMANENT PAPER SIGN

Wikipedia, Acid-free paper, says:

Manufacturers of acid-free paper can indicate the compliance of their product with the test requirements of the ISO 9706 or ANSI Z39.48-1992 standards using a circled infinity symbol (Unicode codepoint 267E, ♾)

The glyph is contained in Deja Vu Sans:

\documentclass{article}
\usepackage{fontspec}
\setmainfont{DejaVuSans.ttf}
\pagestyle{empty}
\begin{document}
^^^^267e
\end{document}

Font XITS/xits-regular.otf:

Font STIXGeneral-Regular/STIXGeneral.otf:

Without a font that contains the symbol, it can be constructed with tikz, for example:

\documentclass{article}
\usepackage{tikz}
\pagestyle{empty}
\begin{document}
\tikz\node[circle,draw,inner sep=.1ex] {$\infty$};
\end{document}

The symbol is in Unicode

U+267E PERMANENT PAPER SIGN

Wikipedia, Acid-free paper, says:

Manufacturers of acid-free paper can indicate the compliance of their product with the test requirements of the ISO 9706 or ANSI Z39.48-1992 standards using a circled infinity symbol (Unicode codepoint 267E, ♾)

I have not found the symbol in The Comprehensive LaTeX Symbol List. There is not a "standard" command in LaTeX for this symbol.

Unicode/OpenType/TrueType fonts

These fonts require LuaLaTeX or XeLaTeX.

The glyph is contained in Deja Vu Sans:

\documentclass{standalone}
\usepackage{fontspec}
\setmainfont{DejaVuSans.ttf}
\pagestyle{empty}
\begin{document}%
^^^^267e%
\end{document}

Font XITS/xits-regular.otf:

Font STIXGeneral-Regular/STIXGeneral.otf:

Solution with TikZ

Without a font that contains the symbol, it can be constructed with tikz, for example:

\documentclass{standalone}
\usepackage{tikz}
\pagestyle{empty}
\begin{document}
\tikz\node[circle,draw,inner sep=.1ex] {$\infty$};
\end{document}

Edit: If you are using LuaLaTeX or XeLaTeX, then the symbol can be used directly as unicode character:

\usepackage{fontspec}
...
\begingroup
  \fontspec{STIXGeneral.otf}
  ♾% or ^^^^267e%
\endgroup

The TikZ solution also works with other TeX compilers.

I have edited the examples to use document class standalone. Thus the examples generate a PDF page with the symbol. The margins are cropped entirely (solution via TikZ) or to the bounding box of the characters (solutions with Unicode fonts). The PDF file can directly be included in pdflatex (or xelatex). Or it can be converted to PostScript to support latex/dvips, e.g. via pdftops of xpdf:

pdftops -eps PermanentPaperSign.pdf PermanentPaperSign.eps

Alternative converters: ghoscript, …

This avoids including a bitmap file (.png).

The symbol is in Unicode

U+267E PERMANENT PAPER SIGN

Wikipedia, Acid-free paper, says:

Manufacturers of acid-free paper can indicate the compliance of their product with the test requirements of the ISO 9706 or ANSI Z39.48-1992 standards using a circled infinity symbol (Unicode codepoint 267E, ♾)

Without a font that contains the symbol, it can be constructed with tikz, for example:

\documentclass{article}
\usepackage{tikz}
\pagestyle{empty}
\begin{document}
\tikz\node[circle,draw,inner sep=.1ex] {$\infty$};
\end{document}

The symbol is in Unicode

U+267E PERMANENT PAPER SIGN

Wikipedia, Acid-free paper, says:

Manufacturers of acid-free paper can indicate the compliance of their product with the test requirements of the ISO 9706 or ANSI Z39.48-1992 standards using a circled infinity symbol (Unicode codepoint 267E, ♾)

The glyph is contained in Deja Vu Sans:

\documentclass{article}
\usepackage{fontspec}
\setmainfont{DejaVuSans.ttf}
\pagestyle{empty}
\begin{document}
^^^^267e
\end{document}

Font XITS/xits-regular.otf:

Font STIXGeneral-Regular/STIXGeneral.otf:

Without a font that contains the symbol, it can be constructed with tikz, for example:

\documentclass{article}
\usepackage{tikz}
\pagestyle{empty}
\begin{document}
\tikz\node[circle,draw,inner sep=.1ex] {$\infty$};
\end{document}