pdfpdftex
After including some figures (saved as .pdfs) in my LaTeX document with \includegraphics, I got the following warning:
pdfTeX warning: pdflatex.exe (file ./figure/figure_1.pdf): PDF inclusion: found PDF version <1.6>, but at most version <1.5> allowed
The strange thing is, I'm using \includegraphics elsewhere in my document for other figures (also saved as .pdfs, in the exact same way), but no warning is generated for those.
What does this mean? How can I make it go away?
The problem is also reported in a german forum mrunix.de. It might be a bug in the tex distribution (pdftex). The problem happens only when you include multiple pdf pages, created in a specific manner (e.g. by MS Office products), in a single page.
Solution: Convert pdf files into ps and then back to pdf using Ghostscript, then the warning will go away (pdf2ps -> ps2pdf). This conversion probably removes the "page group" information from pdf files. (Caveat: This renders your pdf and some text might not be selectable or searchable any more.)
Editing the colorspace of pdf files with ghostscript also resolves the issue (if there is no multiple pages in the pdf file):
gs -o fixed-image.pdf -sDEVICE=pdfwrite -dColorConversionStrategy=/sRGB
-dProcessColorModel=/DeviceRGB original-image.pdf
CMYK conversion if RGB does not work for you:
gs -o fixed-image.pdf -sDEVICE=pdfwrite -dColorConversionStrategy=/CMYK
-dProcessColorModel=/DeviceCMYK original-image.pdf
P.S. Some programs generate "page group"s in pdf files; for example when you impose different images/objects in illustrator or inkscape. It seesm that pdftex is unable to handle multiple page groups in a single output page. The reason might be that each page groups specifies a different color space or transparency space.
Best Answer
By default,
pdflatexwill create a PDF version 1.5 file.It seems that here one of your included PDF graphic is in fact in version 1.6 of the format and therefore has different features which will be lost in included in a pdf file of a previous version.
chances are that the graphic in question do not use any of the features available in PDF 1.6 but that is why there is a warning.
you can either recreate you graphics and if you have that level of control, make sure that it is saved in PDF v1.5, or you can raise the version of your output document to 1.6 by adding in your preamble:
This depends on whether you have any restriction about the output document (some people insist on a specific PDF version).