Preview can easily merge multiple files into a single PDF (say, to combine scanned documents or to combine a PDF with an image). To do it, open the first PDF or image, choose View > Thumbnails, and then drag other files — single or multiple pages of any dimensions — from the desktop onto the thumbnail sidebar. Drag thumbnails to reorder pages within your newly combined PDF and then save the file.
Rotate pages in a PDF
To rotate a single page within a multi-page PDF (handy for scanned receipts), choose View > Thumbnails and then select the thumbnails of the pages you want to rotate. Next, click the Rotate button in the toolbar or choose Tools > Rotate Left or Tools > Rotate Right.
Crop a PDF
If a page in your PDF has extra stuff around it — say, registration or crop marks — you can use the Rectangular Selection tool to crop it. Open the Markup toolbar, click the Rectangular Selection tool, and draw a selection around the area you want to keep. Next, choose Tools > Crop (or press Command-K to commit the crop). To crop multiple pages, choose View > Thumbnails and Command or Shift-click to select multiple thumbnails before committing the crop. To crop all pages, press Command-A to select them before committing the crop. To draw a more accurate selection for cropping, choose Tools > Show Inspector to open the Inspector window, click the Crop icon (it looks like an angled comb), and enter the location and size of the desired crop.
Password-protect a PDF or image
To prevent a PDF or image from being opened, copied from, or printed, try password-protecting it. Open the file and choose File > Export, and in the resulting dialog box choose PDF from the Format menu. Next, enable the Encrypt checkbox, enter a password into the resulting field, and click Save. Be sure to rename or change the location of your newly protected PDF to keep from overwriting your original!
Extract an application icon
Preview can extract several sizes of an application's icon as images. First, select the application wherever it lives in the Finder (say, in your Applications or Downloads folder) and then press Command-C to copy it to your clipboard. Next, press Command-N to create a new document in Preview and all the sizes of the application's icon instantly appear as individual pages with transparency. To save a specific size as a new file, select the appropriate thumbnail and choose File > Export. To preserve the icon's transparent background, choose PNG or TIFF for the file format in the resulting dialog box.
Soft proof your print
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