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I'm running macos Sierra with Preview 9.0 on an iMac. I have a fairly large (40 MB) pdf file that is a version 1.6 PDF. The Preview app does not have a 'save as' option. Your choices under the file menu are: save, duplicate, rename, move to, export, and export as PDF.

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Duplicate makes a copy but it converts PDF from version 1.6 to 1.4 and this in itself reduces file size from 40 MB to 20 MB. 'Move To..' and 'Rename' have no noticeable effect on file or size. Export has several options. The 'None' option, however, also converts file to PDF 1.4 from 1.6 again reducing file size to 20 MB. Export to PDF does the same but file size is 19.5 MB. I'm confused on these differences. It appears just going from PDF 1.6 to PDF 1.4 cuts file size in half. Why is this and why the conversion in 1st place. The only way I know to truly make a copy is do it in Finder using cntrl-c. What info has been lost in going from PDF 1.6 to PDF 1.4?

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To get Save As... on the File menu in Preview, and many other apps as well, press the option key when clicking the menu.

The option key also modifies other commands on different menus as well.

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Note that the shift key also modifies commands in some cases.

  • Save As also coverts file to PDF 1.4 and reduces original to 20 MB. – jmh Sep 4 '17 at 21:05
  • My question was not how to do 'Save As' but why the conversion to PDf 1.4 and the reduction in size by so much. – jmh Sep 4 '17 at 21:09
  • @john, Yeah, I realize that now after reading the entire question, however since you mentioned not having the Save As command I'll let this stay, as it may be helpful to others. – user3439894 Sep 4 '17 at 21:12
  • Sure. Good idea. – jmh Sep 4 '17 at 21:29
  • Many other apps...not all? – DonielF Sep 4 '17 at 22:42
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Each incremental PDF version is just a superset of the preceding version, which adds a few more features to the PDF language 'dictionary'.

A list of the features in each PDF version can be found here.

MacOS saves PDFs using the minimum PDF version required to contain the relevant features. So, if the image requires transparency, it will save to PDF version 1.4. If it doesn't, it will save to v1.3. Encrypting the PDF will raise its version level to 1.6.

MacOS's PDF-creation routines also cannot reproduce all the features in every version of PDF. It cannot do 3D data, for example, which is found in 1.6 and 1.7.

There are many different ways in which the same 'page' can be represented in the PDF format. There are different methods of data compression. Whenever MacOS loads in PDF data and re-saves it, it will change the data stream and re-write the PDF. File copying (Move To.., Rename) will not do this.

In short, PDF file sizes can vary when the data is re-written. You may lose some metadata in the process, but the basic graphical page will be preserved.

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