Using VB.NET PDF SDK
VB.NET PDF Library: how to change pdf page size (width, height) using vb.net
VB.NET Demo Code to change pdf page size (width, height) using vb.net
Change size of a specified page in vb.net
Dim inputFilePath As String = "C:\1.pdf"
Dim outputFilePath As String = "C:\1_new.pdf"
' open the file
Dim doc As PDFDocument = New PDFDocument(inputFilePath)
' get the 2nd page
Dim page As PDFPage = doc.GetPage(1)
' set crop region: start Point(100, 100), width = 300, height = 400
Dim cropArea As RectangleF = New RectangleF(100, 100, 300, 400)
' crop the page
page.Crop(cropArea)
' output the New document
doc.Save(outputFilePath)
Change size for all pages in a document using vb.net
Dim inputFilePath As String = "C:\1.pdf"
Dim outputFilePath As String = "C:\1_new.pdf"
' open the file
Dim doc As PDFDocument = New PDFDocument(inputFilePath)
' set crop region: start Point(100, 100), width = 300, height = 400
Dim cropArea As RectangleF = New RectangleF(100, 100, 300, 400)
' crop pages
doc.CropAllPages(cropArea)
' output the New document
doc.Save(outputFilePath)