Sooner or later every architect needs a smaller copy of a large drawing: an A1 plan for a review meeting printed on A3, or an A0 set sent to a client who only has an A4 printer. Resizing a PDF sounds simple, but a careless resize changes the scale of the drawing, and a drawing at the wrong scale is a drawing that can no longer be measured.
Why the scale changes
A drawing at 1:100 means that 1 unit on paper is 100 units in the building. If you shrink the sheet to half its size, every line is half as long, so 1 unit on the new sheet now stands for 200 units. The drawing is now at 1:200, even though the title block may still say 1:100. This is why resizing needs to be done on purpose, and why the scale note needs updating afterwards.
For example, an A1 sheet is 594 × 841 mm and an A3 sheet is 297 × 420 mm. A3 is almost exactly half of A1 in each direction, so an A1 drawing at 1:100 becomes a drawing at 1:200 on A3. The tool works this out for you, but it is worth knowing the arithmetic so that you can check it.
Paper sizes in the ISO and US families
- ISO A series: A0 is 841 × 1189 mm, A1 is 594 × 841 mm, A2 is 420 × 594 mm, A3 is 297 × 420 mm and A4 is 210 × 297 mm. Every size has the same proportions (1 : 1.414), so a drawing scaled between A sizes fits exactly with no empty margin.
- ARCH series (US): ARCH D is 24 × 36 in and ARCH E is 36 × 48 in. These have proportions of 1 : 1.5 or 1 : 1.33, which are not the same as the A series.
- ANSI series (US): ANSI D is 22 × 34 in and ANSI E is 34 × 44 in.
When you go between families, for example from A1 to ARCH D, the proportions differ, so the drawing is scaled until it fits one side and leaves a margin on the other. That is normal and not a mistake.
How to resize a drawing step by step
- Open the PDF in Resize PDF. The file stays on your computer.
- Choose the new sheet size, for example A3.
- Choose how the drawing fits: scale it to fill the sheet, scale it by a fixed percentage, or keep the drawing at its size and change only the sheet.
- Enter the original scale of the drawing, such as 1:100, and read the new scale the tool reports.
- Download the PDF and update the scale note in the title block and, if there is one, the scale bar.
Keep lines sharp: resize, do not re-print
A common shortcut is to print the PDF to a new PDF using a different paper size. That often turns vector lines into a picture or changes the line weights. Resizing the pages themselves keeps lines and text as vectors, so they stay sharp at any zoom and can still be measured.
Graphic scale bars and numeric scales
A numeric scale such as “1:100” is text and does not change when the drawing is resized. A graphic scale bar is part of the drawing, so it shrinks with it and stays correct. If your drawings carry a graphic scale bar, readers can still take measurements from the resized sheet. If they carry only a numeric scale, update it.
Check the result
- Print at 100% or “actual size”, not “fit to page”, otherwise the printer changes the scale again.
- Measure one known dimension on the new sheet, for example a 3 m wall, with a scale rule or with PDF Measure, and compare it with the expected length at the new scale.
- Check the smallest text and the thinnest lines. Notes that are readable on A1 can become too small on A3.
- To find the smallest sheet that fits a drawing at a given scale, use the Sheet Size Calculator.
Resizing is a convenience for reviews, mock-ups and submissions that allow a reduced copy. For construction issues, always use the sheet size and scale stated in the project documents.