Free Mac OS X PDF Editors

When you need to edit a PDF, you really need to edit a PDF.

The free Preview app that comes with Mac OS X can annotate and do some simple operations on PDF files, but does not have a feature to edit the actual text.

I tried the following free or trial PDF editors on Mac OS X 8.5 for editing text on a 30-page Firefox “print to PDF.”

Product Recommendation Notes
Libre Office for Mac (Open Source) Recommended Does a great job of editing text
iSkysoft PDF Editor Trial Not Recommended Can edit text, but inserts large yellow watermark on save
Inkscape (Open Source) Not Recommended Can only edit first page “due to SVG spec” unless you install plugin


iSkySoft Watermark
iSkySoft Watermark

Multiple page support for Inkscape

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Super Bowl LI 2017

Best Super Bowl that I can remember, with first Super Bowl Overtime.

The New England Patriots (QB Tom Brady) came from behind to win 34-28 over the Atlanta Falcons (QB Matt Ryan).

Atlanta scored 3 TD’s in Q2:

  1. Freeman does 3 drives resulting in a flying landing in the endzone
  2. xxx runs into endzone
  3. did a 82-yard interception.

Patriots got a 41-yard field kick for the 3 points.

Lady Gaga’s half-time performance was good, with surprising acrobatics.

Then the Patriots scored 31 unanswered points to win.

Commercials ($5 million for 30 seconds) weren’t too good, although John Malkovich trying to get his vanity domain from a domain squatter was pretty good (squarespace.com.)

Seemed like mostly cell phone, car and VR-related ads.

W: Super Bowl LI

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Odd but Handy URLs

Organization Link Purpose
Apple http://captive.apple.com/ non-SSL ProbeURL for WiFi hand-shaking. Replaces success.html.
Google http://www.google.com/ncr force plain English site (“no country redirect”)
IANA http://www.example.com official domain for examples in documents
IANA http://www.example.org official domain for examples in documents

How to fix “SuccessSuccess” Wi-Fi issue on MacOS X Mavericks temporally

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SpaceX Launch Begins Era of Space-Based ADS-B Tracking

The big news from the SpaceX launch of 10 Aireon Iridium 2G “Next” satellites is that ADS-B was also included on each satellite.

ADS-B is used for tracking and sending ATC digital information to airplanes. The FAA has mandated that almost all aircraft will install ADS-B transceivers before 2020, at a cost of $5,000 to $1 million per airplane, plus downtime.

Since there’s 150,000 registered US aircraft and thousands of foreign airliners, that just isn’t going to happen with the existing number of Mx shops and remaining 1,080 days. :)

These are fairly large satellites at 860 kg each:




SpaceX Launch Begins Era of Space-Based ADS-B Tracking
Iridium-1 Hosted Webcast
Layman HN Commentary
W: Automatic dependent surveillance – broadcast
faa.gov: ADS-B Frequently Asked Questions (FAQs)
avweb.com: New Satellites Promise Better ATC Coverage
gpsworld.com: Clocks fail on some Galileo satellites, backups working

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Perl and Monotonic Time Functions

Perl on Linux supports the POSIX C clock_gettime() function to get the monotonic time (always increasing system time, except for variable overflow) values:

Comparing monotonic time values:

  • avoid problems with leap seconds going backwards in time by NTP, but can “warp”
  • avoid problems with VM time going backwards
  • can only be used locally, not compared across machines
  • can rollover on variable overflow

Disadvantages of clock_gettime() over time/gmtime:

  • rollover requires awareness and calculation
  • not supported on Mac OS X and buggy before RHEL 5.3
  • relative time, not actual time, so cannot be displayed for humans
  • for most programs, requires code change and re-QA
  • dichotomy still exists between system and database time
use strict;
use diagnostics;

use Time::HiRes qw(clock_gettime CLOCK_REALTIME CLOCK_MONOTONIC);

   my $realtime = clock_gettime(CLOCK_REALTIME);

   my $mono = clock_gettime(CLOCK_MONOTONIC);

   print "realtime = $realtime, monotonic = $mono\n";
$ perl /tmp/clock.pl
realtime = 1483451061.64625, monotonic = 4536159.37919642

Perl – Time::HiRes
clock_gettime(3) – Linux man page
Erlang – Postscript: Time Goes On
lwn.net: The leap second of doom
SO: CLOCK_MONOTONIC Max value
SO: How do I get monotonic time durations in python?
SO: Linux clock_gettime(CLOCK_MONOTONIC) strange non-monotonic behavior
SO: Is CLOCK_MONOTONIC process (or thread) specific?
How the NYE leap second clocked Cloudflare – and how a single character fixed it
Time::Local
W: Swatch Internet Time (Beats)

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