There are a couple of ways to adjust the page size of a document with PDFpen or PDFpenPro.
Saving a document
If you want to retain the original dimensions of your document while saving the same document with different page dimensions, this can be done via the Print dialog:
1. Launch your file in PDFpen/Pro
2. Choose File > PRINT
3. Select a new option under "Paper Size"
4. From the bottom right corner of the Print dialog, choose PDF > "Save as PDF"
The original document will retain its original page size while the newly saved document will have the page size you selected to print to in the Print dialog.
Creating a new document
If you want to create a new document where all pages are a certain size, you would have to set it up before you open/ create a document. For example, to set up a document in ledger-size, landscape:
1. Launch PDFpen/Pro without a document
2. Choose File > New > Blank Document
3. Choose File > Page Setup
4. In the Page Setup dialog, select "Tabloid" and select the "landscape" orientation
Now, if you choose Edit > Insert Blank Page to add a blank page or add subsequent pages from another document, the pages in the document will be as you specified in Page Setup.