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Click the File tab.
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Under Help, click Options, and then click Advanced.
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Next to Image Size and Quality, click the file that you want to turn off picture compression for.
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Under Image Size and Quality, select the Do not compress images in file check box.
To compress a picture or set other picture quality or resolution options, see Reduce the file size of a picture.
https://support.office.com/en-us/article/Turn-off-picture-compression-81a6b603-0266-4451-b08e-fc1bf58da658?ui=en-US&rs=en-US&ad=US&fromAR=1